Lithium transition metal based compound powder, method for manufacturing the same, spray-dried substance serving as firing precursor thereof, lithium secondary battery positive electrode by using the same, and lithium secondary battery

ABSTRACT

A lithium transition metal based compound powder for a lithium secondary battery positive electrode material, characterized by including a lithium transition metal based compound, which has a function of enabling insertion and elimination of lithium ions, as a primary component and being produced by conducting firing after at least one type of compound (hereafter referred to as “Additive 1”) containing at least one type of element (hereafter referred to as “Additive element 1”) selected from B and Bi and at least one type of compound (hereafter referred to as “Additive 2”) containing at least one type of element (hereafter referred to as “Additive element 2”) selected from Mo and W are added in combination to a raw material of the primary component at a ratio of a total of Additive 1 and Additive 2 to a total amount of moles of transition metal elements in the raw material of the primary component of 0.01 percent by mole or more, and less than 2 percent by mole.

TECHNICAL FIELD

The present invention relates to a lithium transition metal basedcompound powder used as a lithium secondary battery positive electrodematerial, a method for manufacturing the same, a spray-dried substanceserving as a firing precursor thereof, a lithium secondary batterypositive electrode by using the lithium transition metal based compoundpowder, and a lithium secondary battery including the lithium secondarybattery positive electrode.

BACKGROUND ART

Lithium secondary batteries have excellent energy densities, outputdensities, and the like and are effective for miniaturization and weightreduction. Therefore the demands therefore as power supplies of portableequipment, e.g., notebook personal computers, cellular phones, and handyvideo cameras, have grown sharply. Furthermore, the lithium secondarybatteries have been also noted as power supplies of electric vehicles(EV), load leveling of electric powers, and the like. In recent years,demands as power supplies of hybrid electric vehicles (HEV) haveexpanded sharply. In particular, in the application to the electricvehicle, excellence is necessary in low cost, safety, life (inparticular at high temperatures), and load characteristics, and animprovement in material has been desired.

Among the materials constituting the lithium secondary battery, as for apositive electrode active material, substances having a function ofenabling elimination and insertion of lithium ions can be used. Thereare various positive electrode active materials having respectivecharacteristics. Furthermore, an enhancement in load characteristics ismentioned as a common issue in facilitating an improvement inperformance, and an improvement in material has been desired intensely.

Moreover, a material exhibiting well-balanced performance as well asexcellence in low cost, safety, and life (in particular at hightemperatures) is desired.

As for the positive electrode active material for the lithium secondarybattery, lithium manganese based composite oxides having a spinelstructure, layer lithium nickel based composite oxides, layer lithiumcobalt based composite oxides, and the like are in practical use atpresent. All lithium secondary batteries by using theselithium-containing composite oxides have advantages and disadvantages incharacteristics. That is, regarding the lithium manganese basedcomposite oxides having a spinel structure, the price is low, thesynthesis is relatively easy, and the safety of batteries produced isexcellent, whereas the capacity is low and the high-temperaturecharacteristics (cycle, preservation) are poor. Regarding the layerlithium nickel based composite oxides, the capacity is high and thehigh-temperature characteristics are excellent, whereas there aredisadvantages in that the synthesis is difficult, the safety ofbatteries produced is poor, the preservation requires caution, and thelike. The layer lithium cobalt based composite oxides are easy tosynthesize and exhibit excellent battery performance balance and,thereby, are widely used as power supplies for portable equipment,whereas there are significant disadvantages in that the safety isunsatisfactory and the cost is high.

Under the above-described present circumstances, a lithium nickelmanganese cobalt based composite oxide having a layer structure has beenproposed as a promising candidate for an active material which overcomesor minimize the disadvantages included in these positive electrodeactive materials and which exhibits excellent battery performancebalance. In particular, demands for cost reduction, demands for increasein voltage, and demands for enhancement of the safety have beenintensified in recent years and, therefore, it is believed that thiscomposite oxide is a promising positive electrode active materialcapable of responding to all needs.

However, the extents of the cost reduction, the increase in voltage, andthe enhancement of the safety are changed depending on the compositionratio. Therefore, in order to respond to demands for further costreduction, use in a higher setting of an upper limit of voltage, and ahigher degree of safety, it is necessary that a composite oxide having acomposition within a limited range is selected and used, for example, amanganese/nickel atomic ratio is specified to be about 1 or more and acobalt ratio is reduced. However, regarding a lithium secondary batteryin which the lithium nickel manganese cobalt based composite oxidehaving a composition within the above-described range is used as apositive electrode material, load characteristics, e.g., rate and outputcharacteristics, and a low-temperature output characteristic become poorand, therefore, further improvement has been required incommercialization.

Incidentally, as for known documents in which a lithium transition metalbased compound is subjected to an introduction treatment of “Additiveelement 1 (B, Bi)” or “Additive element 2 (Mo, W)” shown in the presentinvention, Patent Documents 1 to 24 and Non-Patent Documents 1 to 3, asdescribed below, have been disclosed previously.

Patent Document 1 discloses that a positive electrode containing anactive material, in which a part of Co in LiCoO₂ has been substitutedwith Bi, B, is included.

Patent Document 2 discloses that boron (B) is added to Li_(1-X)CoO₂serving as a positive electrode active material and, thereby, surfacesof grains are covered with boron, the active material is not decomposedat a high voltage, and an excellent charge-discharge cyclecharacteristic is exhibited.

Patent Document 3 discloses that boron (B) or bismuth (Bi) is containedas an element constituting a composite oxide having a layer structure.

Patent Document 4 discloses that a lithium boron cobalt composite oxiderepresented by LiB_(x)Co_((1-x))O₂ (0.001≦x≦0.25) is used as a positiveelectrode active material.

Patent Document 5 discloses a lithium nickel cobalt based compositeoxide containing B as a substitution element.

Patent Document 6 discloses that a positive electrode primarily composedof a composite oxide of lithium and cobalt contains a composite oxide ofBi and lithium.

Patent Document 7 discloses a layer structure oxide which is a layerstructure oxide including a composition represented by a formula AMO₂(A=Li, Na, M=Co, Ni, Fe, Cr) and in which Bi or B in the form of anoxide is present on the surface of this crystallite or betweencrystallites.

Patent Document 8 discloses those in which Li, O, and Mg are specifiedto be indispensable elements as constituent elements of a positiveelectrode active material, a layer or a zigzag layer LiMeO₂ structure isincluded, Me includes at least one type selected from Mn, Co, Ni, andFe, and Mg is present at a position of Li in the LiMeO₂ structure, andthose further containing Mo, or Bi, B as constituent elements.

Patent Document 9 discloses that a positive electrode active materialcovered around with an intermetallic compound or an oxide of B, Bi, Mo,W or the like is used.

Patent Document 10 discloses base grains composed of an oxide of atleast one type of transition element selected from the group consistingof Co, Ni, Mn, and Fe, which contain lithium, wherein a part of or awhole surface is covered with an electrically conductive layer composedof a metal, e.g., Bi.

Patent Document 11 discloses that lithium cobalt oxide or lithium nickeloxide, to which an element, e.g., B, Bi, Mo, or W, is added, is used asa positive electrode active material.

Patent Document 12 discloses that regarding a secondary battery by usinga mixture of lithium manganese oxide and lithium nickel oxide as apositive electrode active material, Bi is contained in a positiveelectrode.

Patent Document 13 discloses that a boron compound is contained in amethod for manufacturing a lithium nickel manganese cobalt basedcomposite oxide.

Patent Document 14 discloses a lithium nickel manganese cobalt basedcomposite oxide, wherein a part of transition metal sites aresubstituted with B.

Patent Document 15 discloses that lithium borate is included on asurface of a lithium nickel manganese cobalt based composite oxidegrains having a layer structure.

Patent Document 16 discloses that a compound of Mo, W, B, or the like isincluded in at least grain surfaces of lithium transition metal basedcomposite oxide having a layer structure.

Patent Document 17 discloses that a mixture containing lithium, nickel,manganese, and boron is fired in a method for manufacturing a lithiumnickel manganese based composite oxide having a layer structure.

Patent Document 18 discloses that a surface of a spinel type lithiummanganese composite oxide is modified by an oxide containing tungsten.

Patent Document 19 and Patent Document 20 disclose that W, and Mo areused as substitution elements for transition metal sites in a lithiumnickel based composite oxide having a layer structure. It is describedthat the heat stability in a charged state is thereby improved.

Patent Document 21 discloses that a lithium nickel manganese cobaltbased composite oxide containing W, Mo is used. It is described that aninexpensive, high-capacity oxide exhibiting excellent heat stability ina charged state as compared with LiCoO₂ is thereby obtained.

Patent Document 22 discloses an example in which a transition metal sitein a lithium nickel manganese cobalt based composite oxide issubstituted with W.

Patent Document 23 discloses that a monoclinic structure lithiummanganese nickel based composite oxide in which transition metal sitesare substituted with Mo, W is used as a positive electrode activematerial. It is described that a lithium secondary battery having a highenergy density and a high voltage and exhibiting high reliability can bethereby provided.

Patent Document 24 discloses that a lithium nickel manganese cobaltbased composite oxide having a layer structure is used.

Non-Patent Document 1 discloses a LiNi_(1/3)Mn_(1/3)Mo_(1/3)O₂ compositeoxide having a layer structure.

Non-Patent Document 2 discloses a material in which a surface ofLiNi_(0.8)Co_(0.2)O₂ is subjected to a covering treatment with Li₂O—B₂O₃glass.

Non-Patent Document 3 discloses that Li[Ni_(x)Co_(1-2x)Mn_(x)]O₂ issubjected to a B₂O₃ addition treatment, and an effect of a sinteringadditive is examined.

Here, regarding Patent Documents 1 to 7, 10, 12 to 15, and 17 to 24 andNon-Patent Documents 1 to 3, there is no description related to additionof Additive 1 and Additive 2 in combination according to the presentinvention and, therefore, it is difficult to achieve objects of thepresent invention.

Furthermore, Patent Documents 8, 9, 11, and 16 describe that bothAdditive element 1 and Additive element 2 are included. Among them,according to Patent Document 8, there is a description of an example inwhich B as Additive element 1 and Mo as Additive element 2 are used incombination. However, the total amount of these elements is a too large2 percent by mole and, in addition, it is necessary that Mg is presentat the Li site. Therefore, there is a problem in that insertion andelimination reactions of lithium during charge and discharge arehindered easily and the performance is not sufficiently improved.

Patent Documents 9 and 11 describe both Additive element 1 and Additiveelement 2, but there is no description that the two are actually used incombination in a positive electrode active material. Furthermore, thereis no description nor indication that such a positive electrode activematerial according to the present invention exhibits high loadcharacteristics.

Patent Document 16 describes that B serves as Additive element 1 and Moor W serves as Additive element 2, but there is no description that thetwo are actually used in combination in a positive electrode activematerial.

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DISCLOSURE OF INVENTION

The present inventors considered that in order to solve an issue ofimprovement of load characteristics, e.g., rate and outputcharacteristics, it is important to allow the crystallinity to becomesufficiently high at the stage of sintering an active material and, inaddition, suppress growth of grains and sintering so as to obtain finegrains and conducted intensive research. As a result, it was found thatregarding especially a layer lithium nickel manganese cobalt basedcomposite oxide, growth of grains and sintering were suppressed and alithium transition metal based compound powder composed of fine grainswere obtained by conducting sintering at a certain temperature or higherafter a compound containing an element of Mo, W, or the like was added.Consequently, regarding the lithium secondary battery positive electrodematerial, besides cost reduction, increase in withstand voltage, andenhancement of safety, the compatibility with the improvement of loadcharacteristics, e.g., rate and output characteristics, was madepossible.

However, in this method, changes in properties, e.g., a reduction inbulk density and an increase in specific surface area, occurred.Consequently, a new problem came up in that handling as a powder andpreparation of electrode became difficult.

Accordingly, it is an object of the present invention to provide alithium transition metal based compound powder for a lithium secondarybattery positive electrode material capable of improving powderproperties while improving load characteristics, e.g., rate and outputcharacteristics, and preferably being compatible with cost reduction,increase in withstand voltage, and enhancement of safety in the use asthe lithium secondary battery positive electrode material, a method formanufacturing the same, a lithium secondary battery positive electrodeby using the lithium transition metal based compound powder, and alithium secondary battery including the lithium secondary batterypositive electrode.

In order to solve the issue of improving powder properties whileimproving load characteristics, e.g., rate and output characteristics,the present inventors conducted intensive research on an improvement inbulk density and optimization of specific surface area. As a result, itwas found that a lithium-containing transition metal based compoundpowder, which was easy to handle and suitable for preparation of anelectrode, was able to be obtained without impairing the above-describedimprovement effects by adding at least one type of compound containingat least one type of element selected from B and Bi and at least onetype of compound containing at least one type of element selected fromMo and W in combination at a predetermined ratio and, thereafter,conducting firing, a lithium transition metal based compound powder,which exhibited excellent powder properties, high load characteristics,high-voltage resistance, and a high degree of safety and which wascapable of reducing the cost, was able to be obtained as a lithiumsecondary battery positive electrode material, and such a lithiumtransition metal based compound powder had a characteristic peak in asurface enhanced Raman spectrum. Consequently, the present invention hasbeen completed.

That is, a lithium transition metal based compound powder for a lithiumsecondary battery positive electrode material according to a firstaspect is characterized by containing a lithium transition metal basedcompound, which has a function of enabling insertion and elimination oflithium ions, as a primary component and having a peak A at 800 cm⁻¹ ormore, and 900 cm⁻¹ or less in a surface enhanced Raman spectrum.

Here, regarding this lithium transition metal based compound powder, itis preferable that the half-width of the peak A is 30 cm⁻¹ or more in asurface enhanced Raman spectrum.

Furthermore, regarding this lithium transition metal based compoundpowder, it is preferable that the intensity of the peak A to theintensity of a peak B in the vicinity of 600±50 cm⁻¹ is larger than 0.04in a surface enhanced Raman spectrum.

Moreover, regarding this lithium transition metal based compound powder,it is preferable that a peak originated from a fragment resulting frombonding between additive elements or between an additive element and anelement constituting a positive electrode active material is observed intime-of-flight secondary ion mass spectrometry.

A lithium transition metal based compound powder for a lithium secondarybattery positive electrode material according to a second aspect ischaracterized in that peaks originated from BWO₅ ⁻ and M′BWO₆ ⁻ (M′represents an element capable of assuming the state of divalent) or BWO₅⁻ and Li₂BWO₆ ⁻ are observed in time-of-flight secondary ion massspectrometry.

A lithium transition metal based compound powder for a lithium secondarybattery positive electrode material according to a third aspect ischaracterized by containing a lithium transition metal based compound,which has a function of enabling insertion and elimination of lithiumions, as a primary component and being produced by conducting firingafter at least one type of compound (hereafter referred to as “Additive1”) containing at least one type of element (hereafter referred to as“Additive element 1”) selected from B and Bi and at least one type ofcompound (hereafter referred to as “Additive 2”) containing at least onetype of element (hereafter referred to as “Additive element 2”) selectedfrom Mo and W are added in combination to a raw material of the primarycomponent at a ratio of a total of Additive 1 and Additive 2 to a totalamount of moles of transition metal elements in the raw material of theprimary component of 0.01 percent by mole or more, and less than 2percent by mole.

Here, regarding this lithium transition metal based compound powder, itis preferable that Additive 1 is selected from boric acid, oxoacidsalts, oxides, and hydroxides.

Regarding this lithium transition metal based compound powder, it ispreferable that Additive 2 is an oxide.

Regarding this lithium transition metal based compound powder, it ispreferable that the ratio of addition of Additive 1 to Additive 2 iswithin the range of 10:1 to 1:20 (molar ratio).

Furthermore, preferably, an atomic ratio of Additive elements 1 in totalto a total of metal elements other than Li, Additive elements 1, andAdditive elements 2 of a surface portion of a primary grain is 20 timesor more larger than the atomic ratio on the whole grain basis.

Preferably, an atomic ratio of Additive elements 2 in total to a totalof metal elements other than Li, Additive elements 1, and Additiveelements 2 of a surface portion of a primary grain is 3 times or morelarger than the atomic ratio on the whole grain basis.

Regarding the lithium transition metal based compound powders accordingto the first to third aspects, it is preferable that median sizesmeasured with a laser diffraction/scattering grain size distributionmeasuring apparatus after 5 minutes of ultrasonic dispersion (output 30W, frequency 22.5 kHz), where the refractive index is set at 1.24 andthe reference of grain size is on a volume basis, are 2 μm or more, and8 μm or less.

Regarding the lithium transition metal based compound powder accordingto the third aspect, it is preferable that the average size of theprimary grain is 0.1 μm or more, and 2 μm or less.

Regarding the lithium transition metal based compound powders accordingto the first to third aspects, it is preferable that the BET specificsurface areas are 0.5 m²/g or more, and 3 m²/g or less.

Regarding the lithium transition metal based compound powders accordingto the first to third aspects, it is preferable that the amounts ofmercury penetration are 0.4 cm³/g or more, and 1.5 cm³/g or less duringpressurization from a pressure of 3.86 kPa to 413 MPa in a mercurypenetration curve based on a mercury penetration method.

Regarding the lithium transition metal based compound powders accordingto the first to third aspects, it is preferable that pore distributioncurves based on the mercury penetration method have at least one mainpeak with a peak top present at a pore radius of 300 nm or more, and1,500 nm or less and have a subpeak with a peak top present at a poreradius of 80 nm or more, and less than 300 nm. In this case, regarding apore distribution curve based on the mercury penetration method, it ispreferable that the pore volume related to the peak with a peak toppresent at a pore radius of 300 nm or more, and 1,500 nm or less is 0.3cm³/g or more, and 0.8 cm³/g or less and the pore volume related to thesubpeak with a peak top present at a pore radius of 80 nm or more, andless than 300 nm is 0.01 cm³/g or more, and 0.3 cm³/g or less.

Regarding the lithium transition metal based compound powders accordingto the first to third aspects, it is preferable that a pore distributioncurves based on the mercury penetration method have at least one mainpeak with a peak top present at a pore radius of 400 nm or more, and1,500 nm or less and have a subpeak with a peak top present at a poreradius of 300 nm or more, and less than 400 nm.

Regarding the lithium transition metal based compound powders accordingto the first to third aspects, it is preferable that the bulk densitiesare 1.2 g/cm³ or more, and 2.0 g/cm³ or less.

Regarding the lithium transition metal based compound powders accordingto the first to third aspects, it is preferable that the volumeresistivities are 1×10³ Ω·cm or more, and 1×10⁷ Ω·cm or less whencompaction is conducted at a pressure of 40 MPa.

Preferably, the lithium transition metal based compound powdersaccording to the first to third aspects contain a lithium nickelmanganese cobalt based composite oxide, which is configured to include acrystal structure belonging to a layer structure, as a primarycomponent.

Furthermore, regarding the above-described lithium transition metalbased compound powders, it is preferable that the compositions arerepresented by Composition formula (I) described below.

LiMo₂  (I)

In formula (I) described above, M represents elements composed of Li,Ni, and Mn or Li, Ni, Mn, and Co, a Mn/Ni molar ratio is 0.1 or more,and 5 or less, a Co/(Mn+Ni+Co) molar ratio is 0 or more, and 0.35 orless, and a Li molar ratio in M is 0.001 or more, and 0.2 or less.

Preferably, the lithium transition metal based compound powder accordingto the present invention having the composition represented byComposition formula (I) described above has been fired at a firingtemperature of 900° C. or higher in an oxygen-containing gas atmosphere.

Regarding the lithium transition metal based compound powder accordingto the present invention having the composition represented byComposition formula (I) described above, it is preferable that when thecarbon content is assumed to be C (percent by weight), the C value is0.005 percent by weight or more, and 0.25 percent by weight or less.

Furthermore, regarding the lithium transition metal based compoundpowder having the composition represented by Composition formula (I)described above, it is preferable that M is represented by Formula (II′)described below.

M=Li_(z′/(2+z′)){(Ni_((1+y′)/2)Mn_((1−y′)/2))_(1-x′)Co_(x′)}_(2/(2+z′))  (II′)

[In Composition formula (II′),

0.1<x′≦0.35

−0.1≦y′≦0.1

(1−x′)(0.02−0.98y′)≦z′≦(1−x′)(0.20−0.88y′)]

Moreover, regarding the lithium transition metal based compound powderhaving the composition represented by Composition formula (I) describedabove, it is preferable that M is represented by Formula (II) describedbelow.

M=Li_(z/(2+z)){(Ni_((1+y)/2)Mn_((1−y)/2))_(1-x)Co_(x)}_(2/(2+z))  (II)

[In Composition formula (II),

0≦x≦0.1

−0.1≦y≦0.1

(1−x)(0.05−0.98y)≦z≦(1−x)(0.20−0.88y)]

Regarding a lithium nickel manganese cobalt based composite oxide powderin which M in Composition formula (I) described above is represented byFormula (II) described above, it is preferable that when the full widthat half maximum of a (110) diffraction peak present at a diffractionangle 2θ in the vicinity of 64.5° in powder X-ray diffractometry byusing CuKα rays is assumed to be FWHM(110), 0.01≦FWHM(110)≦0.3 holds.

Furthermore, in powder X-ray diffractometry by using CuKα rays of alithium nickel manganese cobalt based composite oxide powder in which Min Composition formula (I) described above is represented by Formula(II) described above, it is preferable that regarding a (018)diffraction peak present at a diffraction angle 2θ in the vicinity of64°, a (110) diffraction peak present in the vicinity of 64.5°, and a(113) diffraction peak present in the vicinity of 68°, no diffractionpeak originated from a heterogeneous phase is present on the side at anangle higher than the angle of each peak top, or in the case wherediffraction peaks originated from heterogeneous phases are present, theratio of the integrated intensity of heterogeneous phase peaks to thatof the diffraction peak of each intrinsic crystal phase is within thefollowing range.

0≦I₀₁₈*/I₀₁₈≦0.20

0≦I₁₁₀*/I₁₁₀≦0.25

0≦I₁₁₃*/I₁₁₃≦0.30

(Here, I₀₁₈, I₁₁₀, and I₁₁₃ represent integrated intensities of the(018), (110), and (113) diffraction peaks, respectively, and I₀₁₈*,I₁₁₀*, and I₁₁₃* represent integrated intensities of the diffractionpeaks originated from heterogeneous phases and observed on the sides atangles higher than the angles of peak tops of the (018), (110), and(113) diffraction peaks, respectively.)

A method for manufacturing a lithium transition metal based compoundpowder for a lithium secondary battery positive electrode materialaccording to a forth aspect is a method for manufacturing theabove-described lithium transition metal based compound powder and ischaracterized by including the steps of pulverizing a lithium compound,at least one type of transition metal compound selected from V, Cr, Mn,Fe, Co, Ni, and Cu, Additive 1, and Additive 2 in a liquid medium andspray-drying a slurry in which they are dispersed homogeneously in aspray-drying step and firing the resulting spray-dried substance in afiring step.

In the method for manufacturing a lithium transition metal basedcompound powder according to the fourth aspect, it is preferable thatregarding a slurry preparation step, the lithium compound, theabove-described transition metal compound, Additive 1 described above,and Additive 2 described above are pulverized in the liquid medium untilthe median size measured with a laser diffraction/scattering grain sizedistribution measuring apparatus after 5 minutes of ultrasonicdispersion (output 30 W, frequency 22.5 kHz) reaches 0.4 μm or less,where the refractive index is set at 1.24 and the reference of grainsize is on a volume basis, and regarding the spray-drying step, spraydrying is conducted under a condition in which 50 cp≦V≦4,000 cp and500≦G/S≦10,000 hold, where V (cp) represents a slurry viscosity, S(L/min) represents an amount of supply of slurry, and G (L/min)represents an amount of supply of gas in the spray drying.

In the method for manufacturing a lithium transition metal basedcompound powder according to the fourth aspect, it is preferable thatthe above-described transition metal compound contains at least a nickelcompound, a manganese compound, and a cobalt compound and regarding theabove-described firing step, the above-described spray-dried substanceis fired at a firing temperature of 900° C. or higher in anoxygen-containing gas atmosphere.

Furthermore, in the method for manufacturing a lithium transition metalbased compound powder according to the fourth aspect, it is preferablethat a raw material used for the lithium compound is lithium carbonate.

A spray-dried substance, which is a precursor of a lithium transitionmetal based compound powder for a lithium secondary battery positiveelectrode material, according to a fifth aspect is characterized bybeing a spray-dried substance serving as a precursor of a lithiumtransition metal based compound powder for a lithium secondary batterypositive electrode material and being obtained by pulverizing a lithiumcompound, at least one type of transition metal compound selected fromV, Cr, Mn, Fe, Co, Ni, and Cu, Additive 1, and Additive 2 in a liquidmedium and spray-drying a slurry prepared by dispersing themhomogeneously, wherein the median size of the spray-dried substancemeasured with a laser diffraction/scattering grain size distributionmeasuring apparatus after 5 minutes of ultrasonic dispersion (output 30W, frequency 22.5 kHz) is 0.1 μm or more, and 4 μm or less, where therefractive index is set at 1.24 and the reference of grain size is on avolume basis.

Furthermore, regarding the spray-dried substance according to the fifthaspect, it is preferable that the BET specific surface area is 10 m²/gor more, and 100 m²/g or less.

A lithium secondary battery positive electrode according to a sixthaspect is characterized by including a positive electrode activematerial layer containing the lithium transition metal based compoundpowder according to the above-described first to third aspects and abinder on a collector.

A lithium secondary battery according to a seventh aspect ischaracterized by including a negative electrode capable of absorbing andreleasing lithium, a non-aqueous electrolyte containing a lithium salt,and a positive electrode capable of absorbing and releasing lithium,wherein the lithium secondary battery positive electrode according tothe above-described sixth aspect is used as the positive electrode.

In the case where the lithium transition metal based compound powdersfor a lithium secondary battery positive electrode material according tothe first to the third aspects are used as lithium secondary batterypositive electrodes, compatibility of cost reduction and enhancement ofsafety with high load characteristics and improvement in powderhandleability can be ensured. Consequently, according to the presentinvention, an inexpensive lithium secondary battery which exhibitsexcellent handleability and a high degree of safety and which deliversexcellent performance even in the use at a high charge voltage isprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Example 1.

FIG. 2 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Example 2.

FIG. 3 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Example 3.

FIG. 4 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Example 4.

FIG. 5 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Example 5.

FIG. 6 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Comparativeexample 1.

FIG. 7 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Comparativeexample 2.

FIG. 8 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Comparativeexample 3.

FIG. 9 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Comparativeexample 4.

FIG. 10 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Comparativeexample 5.

FIG. 11 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Comparativeexample 6.

FIG. 12 is a graph showing the pore distribution curve of a lithiumnickel manganese cobalt composite oxide powder produced in Comparativeexample 7.

FIG. 13 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Example 1.

FIG. 14 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Example 2.

FIG. 15 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Example 3.

FIG. 16 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Example 4.

FIG. 17 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Example 5.

FIG. 18 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Comparativeexample 1.

FIG. 19 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Comparativeexample 2.

FIG. 20 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Comparativeexample 3.

FIG. 21 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Comparativeexample 4.

FIG. 22 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Comparativeexample 5.

FIG. 23 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Comparativeexample 6.

FIG. 24 is a SEM image (photograph) (magnification ×10,000) of thelithium nickel manganese cobalt composite oxide produced in Comparativeexample 7.

FIG. 25 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Example 1.

FIG. 26 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Example 2.

FIG. 27 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Example 3.

FIG. 28 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Example 4.

FIG. 29 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Example 5.

FIG. 30 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Comparative example 1.

FIG. 31 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Comparative example 2.

FIG. 32 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Comparative example 3.

FIG. 33 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Comparative example 4.

FIG. 34 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Comparative example 5.

FIG. 35 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Comparative example 6.

FIG. 36 is a graph showing the XRD pattern of the lithium nickelmanganese cobalt composite oxide produced in Comparative example 7.

FIG. 37 is a graph showing the SERS pattern of a lithium transitionmetal based compound powder produced in Example 1.

FIG. 38 is a graph showing the SERS pattern of a lithium transitionmetal based compound powder produced in Example 2.

FIG. 39 is a graph showing the SERS pattern of a lithium transitionmetal based compound powder produced in Example 3.

FIG. 40 is a graph showing the SERS pattern of a lithium transitionmetal based compound powder produced in Example 4.

FIG. 41 is a graph showing the SERS pattern of a lithium transitionmetal based compound powder produced in Example 5.

FIG. 42 is a graph showing the ToF-SIMS pattern of the lithiumtransition metal based compound powder produced in Example 1. FIG. 42(a)shows the theoretical pattern for BWO5⁻ and six peaks originating fromBWO₅ ⁻ detected within the mass number from 272 to 277. FIG. 42(b) showsthat a group of peaks originating from M′BWO₆ ⁻ were also detected, andparticularly intense five peaks were detected within the mass numberfrom 344 to 348.

DETAILED DESCRIPTIONS

The embodiments according to the present invention will be describedbelow in detail. However, the explanation of the constituent featuresdescribed below is an example (typical example) of execution forms ofthe present invention, and the present invention is not limited to thesecontents.

[Lithium Transition Metal Based Compound Powder]

As described above, a lithium transition metal based compound powder fora lithium secondary battery positive electrode material according to thepresent invention (hereafter may be referred to as a “positive electrodeactive material according to the present invention”) is characterized byhaving a peak A at 800 cm⁻¹ or more, and 900 cm⁻¹ or less in a surfaceenhanced Raman spectrum.

Here, the surface enhanced Raman spectroscopy (hereafter abbreviated asSERS) is a technique in which a noble metal, e.g., silver, is thinlyevaporated on a sample surface in the manner of sea-island so as toselectively amplify a Raman spectrum originated from molecular vibrationof an outermost surface of the sample. In common Raman spectroscopy, itis believed that the detection depth is about 0.1 to 1 μm. However, inSERS, signals of surface layer portion in contact with noble metalgrains constitute a most part.

In the present invention, the peak A is present at 800 cm⁻¹ or more, and900 cm⁻¹ or less in the SERS spectrum. The position of the peak A isusually at 800 cm⁻¹ or more, preferably 810 cm⁻¹ or more, morepreferably 820 cm⁻¹ or more, further preferably 830 cm⁻¹ or more, andmost preferably 840 cm⁻¹ or more, and usually at 900 cm⁻¹ or less,preferably 895 cm⁻¹ or less, more preferably 890 cm⁻¹ or less, and mostpreferably 885 cm⁻¹ or less. If the position is out of this range, theeffects of the present invention may not be exerted sufficiently.

Furthermore, as described above, in SERS of the positive electrodeactive material according to the present invention, it is preferablethat the half-width of the above-described peak A is 30 cm⁻¹ or more,and further preferably 60 cm⁻¹ or more. It is estimated that a broadpeak having such a half-width is originated from chemical changes ofadditive elements due to interactions with the elements in the positiveelectrode active material. In the case where the half-width of the peakA is out of the above-described range, that is, in the case where theinteraction between the additive elements and the elements in thepositive electrode active material is small, the effects of the presentinvention may not be exerted sufficiently. Incidentally, the additiveelement here is synonymous with an additive element described later.

Moreover, as described above, regarding the positive electrode activematerial according to the present invention, it is preferable that theintensity of the peak A to the intensity of a peak B at 600±50 cm⁻¹ islarger than 0.04, further preferably 0.05 or more in SERS. Here, thepeak B at 600±50 cm⁻¹ is a peak originated from stretching vibration ofM″O_(A) (M″ represents a metal element in the positive electrode activematerial). In the case where the intensity of the peak A to theintensity of the peak B is small, the effects of the present inventionmay not be exerted sufficiently.

In addition, as described above, in time-of-flight secondary ion massspectrometry (hereafter abbreviated as ToF-SIMS) of the positiveelectrode active material according to the present invention, it ispreferable that a peak originated from a fragment resulting from bondingbetween the additive elements or between the additive element and theelement constituting the positive electrode active material is observed.

Here, ToF-SIMS is a technique in which a sample is irradiated with ionbeams, generated secondary ions are detected with a time-of-flight massspectroscope and, thereby, chemical species present at the outermostsurface of the sample are estimated. According to this method, thedistribution state of additive elements present in the vicinity of thesurface layer can be estimated. In the case where no peak originatedfrom a fragment resulting from bonding between the additive elements orbetween the additive element and the element in the positive electrodeactive material is observed, the dispersion of the additive elements maynot be sufficient and the effects of the present invention may not beexerted sufficiently.

Incidentally, the lithium transition metal based compound powder for alithium secondary battery positive electrode material according to thepresent invention is characterized in that when B and W are used asadditive elements, peaks originated from BWO₅ ⁻ and M′BWO₆ ⁻ (M′represents an element capable of assuming the state of divalent) or BWO₅⁻ and Li₂BWO₆ ⁻ are observed in ToF-SIMS. In the case where theabove-described peaks are not observed, the dispersion of the additiveelements may not be sufficient and the effects of the present inventionmay not be exerted sufficiently.

The positive electrode material according to the present invention ischaracterized by containing the lithium transition metal based compound,which has the function of enabling insertion and elimination of lithiumions, as a primary component and being produced by conducting firingafter at least one type of compound (hereafter referred to as “Additive1”) containing at least one type of element (hereafter referred to as“Additive element 1”) selected from B and Bi and at least one type ofcompound (hereafter referred to as “Additive 2”) containing at least onetype of element (hereafter referred to as “Additive element 2”) selectedfrom Mo and W are added in combination to the raw material of theprimary component at a ratio of a total of Additive 1 and Additive 2 toa total amount of moles of transition metal elements in the raw materialof the primary component of 0.01 percent by mole or more, and less than2 percent by mole.

<Lithium-Containing Transition Metal Compound>

The lithium transition metal based compound according to the presentinvention refers to a compound having a structure enabling eliminationand insertion of Li ions. Examples thereof include sulfides, phosphatecompounds, and lithium transition metal composite oxides. Examples ofsulfides include compounds, e.g., TiS₂ and MoS₂, having atwo-dimensional layer structure and Chevrel compounds represented by ageneral formula Me_(x)Mo₆S₈ (Me represents Pb, Ag, Cu, and other varioustransition metals), which have a strong three-dimensional skeletonstructure. Examples of phosphate compounds include compounds belongingto an olivine structure and, in general, is represented by LiMePO₄ (Merepresents at least one type of transition metal). Specific examplesinclude LiFePO₄, LiCoPO₄, LiNiPO₄, and LiMnPO₄. Examples of lithiumtransition metal composite oxides include composite oxides belonging toa spinel structure enabling three-dimensional diffusion and compositeoxides belonging to a layer structure enabling two-dimensional diffusionof lithium ions. In general, the composite oxides having the spinelstructure are represented by LiMe₂O₄(Me represents at least one type oftransition metal). Specific examples thereof include LiMn₂O₄, LiCoMnO₄,LiNi_(0.5)Mn_(1.5)O₄, and CoLiVO₄. In general, the composite oxideshaving the layer structure are represented by LiMeO₂ (Me represents atleast one type of transition metal). Specific examples thereof includeLiCoO₂, LiNiO₂, LiNi_(1-x)Co_(x)O₂, LiNi_(1-x-y)Co_(x)Mn_(y)O₂,LiNi_(0.5)Mn_(0.5)O₂, Li_(1.2)Cr_(0.4)Mn_(0.4)O₂,Li_(1.2)Cr_(0.4)Ti_(0.4)O₂, and LiMnO₂.

Preferably, the lithium transition metal based compound powder accordingto the present invention is configured to include a crystal structurebelonging to the olivine structure, the spinel structure, or the layerstructure from the viewpoint of diffusion of lithium ions. Most of all,compound powders configured to include a crystal structure belonging tothe layer structure are particularly preferable.

Furthermore, foreign elements may be introduced in the lithiumtransition metal based compound powder according to the presentinvention. The foreign element is selected from at least one type of Na,Mg, Al, Si, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Ru, Rh,Pd, Ag, In, Sn, Sb, Te, Ba, Ta, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, N, F, P, S, Cl, Br, and I. Theseforeign elements may be taken into a crystal structure of the lithiumnickel manganese cobalt based composite oxide or may not be taken intothe crystal structure of the lithium nickel manganese cobalt basedcomposite oxide but be unevenly distributed as simple substances orcompounds on grain surfaces thereof or at crystal grain boundaries.

The present invention is characterized in that at least one typeselected from B and Bi is used as Additive element 1. Among theseAdditive elements 1, it is preferable that Additive element 1 is B fromthe viewpoint of being available as an industrial raw materialinexpensively and being a light element.

Regarding the type of compound (Additive 1) containing Additive element1, the type thereof is not specifically limited insofar as the effect ofthe present invention are exerted. Usually, boric acid, oxoacid salts,oxides, hydroxides, and the like are used. Among these Additives 1,boric acid and oxides are preferable from the viewpoint of beingavailable as an industrial raw material inexpensively, and boric acid isparticularly preferable.

Examples of compounds serving as Additives 1 include BO, B₂O₂, B₂O₃,B₄O₅, B₆O, B₇O, B₁₃O₂, LiBO₂, LiB₅O₈, Li₂B₄O₇, HBO₂, H₃BO₃, B(OH)₃,B(OH)₄, BiBO₃, Bi₂O₃, Bi₂O₅, and Bi(OH)₃. Preferable examples includeB₂O₃, H₃BO₃, and Bi₂O₃ from the viewpoint of being available as anindustrial raw material relatively inexpensively and easily, and HBO₃ isparticularly preferable. These Additive 1 may be used alone, or at leasttwo types may be used in combination.

The present invention is characterized in that at least one typeselected from Mo and W is used as Additive element 2. Among theseAdditive elements 2, it is preferable that Additive element 2 is W fromthe viewpoint of a significant effect.

Regarding the type of compound (Additive 2) containing Additive element2, the type thereof is not specifically limited insofar as the effect ofthe present invention are exerted. Usually, oxides are used.

Examples of compounds serving as Additives 2 include MoO, MoO₂, MoO₃,MoO_(x), Mo₂O₃, Mo₂O₅, Li₂MoO₄, WO, WO₂, WO₃, WO_(x), W₂O₃, W₂O₅,W₁₈O₄₉, W₂₀O₅₈, W₂₄O₇₀, W₂₅O₇₃, W₄₀O₁₁₈, and Li₂WO₄. Preferable examplesinclude MOO₃, Li₂MoO₄, WO₃, and Li₂WO₄ from the viewpoint of beingavailable as an industrial raw material relatively easily or containinglithium, and WO₃ is particularly preferable. One type of these Additives2 may be used alone, or at least two types may be used in combination.

The range of the amount of addition of a total of Additive 1 andAdditive 2 relative to a total amount of moles of transition metalelements constituting the primary component is usually 0.01 percent bymole or more, and less than 2 percent by mole, preferably 0.03 percentby mole or more, and less than 1.8 percent by mole, more preferably 0.04percent by mole or more, and less than 1.6 percent by mole, andparticularly preferably 0.05 percent by mole or more, and less than 1.5percent by mole. If the amount is less than the lower limit, theabove-described effects may not be exerted. If the amount exceeds theupper limit, deterioration of the battery performance may result.

The range of the ratio of addition of Additive 1 to Additive 2 isusually 10:1 or more, and 1:20 or less on a molar ratio basis,preferably 5:1 or more, and 1:15 or less, more preferably 2:1 or more,and 1:10 or less, and particularly preferably 1:1 or more, and 1:5 orless. If the ratio is out of this range, the effect of the presentinvention may not be easily exerted.

The lithium transition metal based compound powder according to thepresent invention is characterized in that elements (Additive elements)derived from Additives, that is, at least one type selected from B andBi (Additive element 1) and Mo and W (Additive element 2), is presentthrough concentration on a surface portion of a primary grain thereof.Specifically, an atomic ratio of Additive elements 1 in total to a totalof metal elements except Li, Additive elements 1, and Additive elements2 (that is, other than Li, Additive elements 1, and Additive elements 2)of the surface portion of the primary grain is usually 20 times or morelarger than the atomic ratio on the whole grain basis. Preferably, thelower limit of this ratio is 30 times or more, more preferably 40 timesor more, and particularly preferably 50 times or more. Usually the upperlimit is not specifically limited. However 500 times or less ispreferable, 400 times or more is more preferable, 300 times or more isparticularly preferable, and 200 times or less is most preferable. Ifthis ratio is too small, an effect of improving the powder properties issmall. In contrast, if the ratio is too large, deterioration of thebattery performance may result.

Furthermore, usually, a molar ratio of Additive element 2 to a total ofmetal elements except Li, Additive elements 1, and Additive elements 2(that is, other than Li, Additive elements 1, and Additive elements 2)of the surface portion of the primary grain is 3 times or more largerthan the atomic ratio on the whole grain basis. Preferably, the lowerlimit of this ratio is 4 times or more, more preferably 5 times or more,and particularly preferably 6 times or more. Usually the upper limit isnot specifically limited. However 150 times or less is preferable, 100times or less is more preferable, 50 times or more is particularlypreferable, and 30 times or less is most preferable. If this ratio istoo small, an effect of improving the battery performance is small. Incontrast, if the ratio is too large, deterioration of the batteryperformance may result.

The analysis of the composition of the surface portion of the primarygrain of the lithium transition metal based compound powder is conductedby X-ray photoelectron spectroscopy (XPS) under the condition in whichmonochromatic ray AlKα is used as an X-ray source, an analysis area is0.8 mm diameter, and take-off angle is 65°. The analyzable range (depth)is different depending on the composition of the primary grain. Usually,the range is 0.1 nm or more, and 50 nm or less. In particular, regardingthe positive electrode active material, the range is usually 1 nm ormore, and 10 nm or less. Therefore, in the present invention, thesurface portion of the primary grain of the lithium transition metalbased compound powder refers to the range measurable under thiscondition.

<Median Size and 90 Percent Cumulative Diameter (D₉₀)>

The median size of the lithium transition metal based compound powderaccording to the present invention is usually 2 μm or more, preferably2.5 μm or more, more preferably 3 μm or more, further preferably 3.5 μmor more, and most preferably 4 μm or more, and usually 8 μm or less,preferably 7.5 μm or less, more preferably 7 μm or less, furtherpreferably 6.5 μm or less, and most preferably 6 μm or less. If themedian size is smaller than this lower limit, a problem may occur in thecoating performance in formation of the positive electrode activematerial layer. If the median size exceeds the upper limit,deterioration of the battery performance may result.

Furthermore, the 90 percent cumulative diameter (D₉₀) of a secondarygrain of the lithium transition metal based compound powder according tothe present invention is usually 15 μm or less, preferably 12 μm orless, more preferably 10 μm or less, and most preferably 8 μm or less,and usually 3 μm or more, preferably 4 μm or more, more preferably 5 μmor more, and most preferably 6 μm or more. If the 90 percent cumulativediameter (D₉₀) exceeds the above-described upper limit, deterioration ofthe battery performance may result. If the 90 percent cumulativediameter (D₉₀) is smaller than the lower limit, a problem may occur inthe coating performance in formation of the positive electrode activematerial layer.

Incidentally, in the present invention, the median size serving as anaverage grain size and the 90 percent cumulative diameter (D₉₀) aremeasured with a known laser diffraction/scattering grain sizedistribution measuring apparatus, where the refractive index is set at1.24 and the reference of grain size is on a volume basis. In thepresent invention, a 0.1 percent by weight sodium hexametaphosphateaqueous solution is used as a dispersion medium used in the measurement,and measurement is conducted after 5 minutes of ultrasonic dispersion(output 30 W, frequency 22.5 kHz).

<Average Primary Grain Size>

The average size (average primary grain size) of the lithium transitionmetal based compound powder according to the present invention is notspecifically limited. However, the lower limit is preferably 0.1 μm ormore, more preferably 0.2 μm or more, and most preferably 0.3 μm ormore, and the upper limit is preferably 2 μm or less, more preferably1.5 μm or less, further preferably 1 μm or less, and most preferably 0.9μm or less. If the average primary grain size exceeds theabove-described upper limit, the powder filling performance is adverselyaffected, and the specific surface area is reduced. Consequently, thereis a possibility that the battery performance, e.g., a ratecharacteristic and an output characteristic, may deteriorate. If theaverage primary grain size is smaller than the above-described lowerlimit, the crystal is undeveloped and, therefore, problems may occur inthat, for example, reversibility of charge and discharge becomes poor.

The average primary grain size in the present invention refers to anaverage size observed with a scanning electron microscope (SEM) and canbe determined as an average value of about 10 to 30 primary grains byusing a SEM image magnified by 30,000 times.

<BET Specific Surface Area>

Furthermore, the BET specific surface area of the lithium transitionmetal based compound powder according to the present invention isusually 0.5 m²/g or more, preferably 0.6 m²/g or more, furtherpreferably 0.8 m²/g or more, and most preferably 1.0 m²/g or more, andusually 3 m²/g or less, preferably 2.8 m²/g or less, further preferably2.5 m²/g or less, and most preferably 2.0 m²/g or less. If the BETspecific surface area is smaller than this range, the batteryperformance deteriorates easily. If the BET specific surface area islarger than this range, the bulk density does not increase easily and aproblem may occur in the coating performance in formation of thepositive electrode active material.

The BET specific surface area can be measured with a known BET powderspecific surface area measuring apparatus. In the present invention,AMS8000 Automatic powder specific surface area measuring apparatus:produced by OHKURA RIKEN CO., LTD., was used, nitrogen was used as anadsorption gas, helium was used as a carrier gas, and the measurementwas conducted by a BET single point method based on a continuous flowmethod. Specifically, a powder sample was heat-deaerated with a mixedgas at a temperature of 150° C. Then, cooling is conducted to a liquidnitrogen temperature so that the mixed gas was adsorbed. Thereafter, thetemperature of this was raised to room temperature with water and,thereby, the adsorbed nitrogen was desorbed. The amount thereof wasdetected with a thermal conductivity detector and the specific surfacearea of the sample was calculated therefrom.

<Pore Characteristics Based on Mercury Penetration Method>

Preferably, the lithium transition metal based compound powder for alithium secondary battery positive electrode material according to thepresent invention satisfies specific condition in a measurement based ona mercury penetration method.

The mercury penetration method adopted for an evaluation of the lithiumtransition metal based compound powder according to the presentinvention will be described below.

The mercury penetration method is a technique in which mercury isallowed to penetrate into pores of a sample, e.g., porous grains, whilea pressure is applied, so as to obtain information, e.g., a specificsurface area and pore size distribution, from the relationship betweenthe pressure and the amount of mercury penetration.

Specifically, the inside of a container including a sample is evacuatedand, thereafter, the inside of the container is filled with mercury.Since mercury has a high surface tension, mercury does not penetratepores of the sample surface on an “as-is” basis. However, when apressure is applied to mercury and the pressure is gradually increased,mercury gradually penetrates the pores sequentially from large-sizepores to small-size pores. A mercury penetration curve indicating therelationship between the pressure applied to mercury and the amount ofmercury penetration is obtained by detecting changes in a liquid levelof mercury (that is, the amount of mercury penetration into pores) whilethe pressure is increased continuously.

Here, the shape of a pore is assumed to be cylindrical, and when theradius thereof is represented by r, the surface tension of mercury isrepresented by δ, and the contact angle is represented by θ, themagnitude in a direction of pushing mercury out of the pore isrepresented by −2πrδ(cos θ) (when θ>90°, this takes on a positivevalue). Furthermore, the magnitude of a force in a direction of pushingmercury into the pore at a pressure of P is represented by πr²P.Therefore, Mathematical expression (1) and Mathematical expression (2),as described below, are derived on the basis of a balance between theseforces.

−2πrδ(cos θ)=πr ² P  (1)

Pr=−2δ(cos θ)  (2)

Regarding mercury, in general, the value of surface tension=about 480dyn/cm and the value of contact angle=about 140° are used frequently. Inthe case where these values are used, the radius of pore, into whichmercury is penetrated at a pressure of P, is represented by Mathematicalexpression (3) as described below.

$\begin{matrix}\left\lbrack {{Mathematical}\mspace{14mu} {formula}\mspace{14mu} 1} \right\rbrack & \; \\{{r\mspace{14mu} ({nm})} = \frac{7.5 \times 10^{8}}{P\mspace{14mu} ({Pa})}} & (3)\end{matrix}$

That is, since there is an interrelation between the pressure P appliedto mercury and the radius r of the pore, into which mercury ispenetrated, a pore distribution curve indicating the relationshipbetween the dimension of the pore radius of the sample and the volumethereof can be obtained on the basis of the resulting mercurypenetration curve. For example, when the pressure P is changed from 0.1MPa to 100 MPa, the measurement can be conducted with respect to thepores within the range of about 7,500 nm to about 7.5 nm.

Regarding the rough measurement limit of the pore radius by the mercurypenetration method, the lower limit is about 2 nm or more, and the upperlimit is about 200 μm or less. Therefore, it can be said that themercury penetration method is suitable for the analysis of the poredistribution in a relatively large pore radius range as compared with anitrogen adsorption method described later.

The measurement by the mercury penetration method can be conducted byusing an apparatus, e.g., a mercury porosimeter. Specific examples ofmercury porosimeters include AutoPore produced by Micromeritics andPoreMaster produced by Quantachrome.

Regarding the lithium transition metal based compound powder accordingto the present invention, it is preferable that the amount of mercurypenetration is 0.4 cm³/g or more, and 1.5 cm³/g or less duringpressurization from a pressure of 3.86 kPa to 413 MPa in the mercurypenetration curve based on the mercury penetration method. The amount ofmercury penetration is more preferably 0.45 cm³/g or more, mostpreferably 0.5 cm³/g or more, and more preferably 1.4 cm³/g or less,further preferably 1.3 cm³/g or less, and most preferably 1.2 cm³/g orless. If the upper limit of this range is exceeded, voids become toomuch, and in the case where the lithium transition metal based compoundpowder according to the present invention is used as a positiveelectrode material, the filling factor of the positive electrode activematerial into a positive electrode plate is reduced and, thereby, thebattery capacity is limited. On the other hand, if the amount is lessthan the lower limit of this range, voids between grains become toosmall and, therefore, in the case where a battery is produced while thelithium transition metal based compound powder according to the presentinvention is used as the positive electrode material, lithium diffusionbetween grains is inhibited and the load characteristics deteriorate.

Regarding the lithium transition metal based compound powders accordingto the present invention, in the case where the pore distribution curveis measured by the above-described mercury penetration method, usually,a specific main peak, as described below, appears.

In the present specification, the “pore distribution curve” refers to aplot, where the horizontal axis indicates the pore radius and thevertical axis indicates the value of a total pore volume per unit weight(usually 1 g) of pores having radii larger than or equal to the radiuson the horizontal axis, the value of total pore volume beingdifferentiated with respect to the logarithm of the pore radius.Usually, plotted points are bonded and represented as a graph. Inparticular, the pore distribution curve obtained by measuring thelithium transition metal based compound powder according to the presentinvention by the mercury penetration method is appropriately referred toas a “pore distribution curve according to the present invention” in thedescription hereafter.

Incidentally, in the present specification, a “main peak” refers to alargest peak among peaks included in the pore distribution curve. A“subpeak” refers to a peak other than the main peak included in the poredistribution curve.

In the present specification, a “peak top” refers to a point which takeson a largest coordinate value with respect to the vertical axis in eachpeak included in the pore distribution curve.

<Main Peak>

Regarding a main peak included in the pore distribution curve accordingto the present invention, the peak top thereof is present at a poreradius within the range of usually 300 nm or more, more preferably 500nm or more, and most preferably 700 nm or more, and usually 1,500 nm orless, preferably 1,200 nm or less, more preferably 1,000 nm or less,further preferably 980 nm or less, and most preferably 950 nm or less.If the upper limit of this range is exceeded, in the case where abattery is produced while the lithium transition metal based compoundpowder according to the present invention is used as the positiveelectrode material, lithium diffusion in the positive electrode materialis inhibited or there is a shortage of conduction path, so that the loadcharacteristics may deteriorate. On the other hand, if the pore radiusis smaller than the lower limit of this range, in the case where apositive electrode is produced by using the lithium transition metalbased compound powder according to the present invention, the amounts ofrequired conductive material and binder increase, so that the fillingfactor of the active material into a positive electrode plate (collectorof positive electrode) may be limited and, thereby, the battery capacitymay be limited. Furthermore, as grains are made finer, in preparation ofa paint, the mechanical property of a coating film becomes hard orbrittle, peeling of the coating film may occur easily in a winding stepduring battery assembly.

Moreover, regarding a pore distribution curve according to the presentinvention, it is favorable that the pore volume related to the peak witha peak top present at a pore radius of 300 nm or more, and 1,500 nm orless is usually 0.3 cm³/g or more, preferably 0.32 cm³/g or more, morepreferably 0.34 cm³/g or more, and most preferably 0.35 cm³/g or, andusually 0.8 cm³/g or less, preferably 0.7 cm³/g or less, more preferably0.6 cm³/g or less, and most preferably, 0.5 cm³/g or less. If the upperlimit of this range is exceeded, voids become too much, and in the casewhere the lithium transition metal based compound powder according tothe present invention is used as a positive electrode material, thefilling factor of the positive electrode active material into a positiveelectrode plate is reduced and, thereby, the battery capacity may belimited. On the other hand, if the pore volume is less than the lowerlimit of this range, voids between grains become too small and,therefore, in the case where a battery is produced while the lithiumtransition metal based compound powder according to the presentinvention is used as the positive electrode material, lithium diffusionbetween secondary grains is inhibited and the load characteristics maydeteriorate.

<Subpeak>

The pore distribution curve according to the present invention may havea plurality of subpeaks in addition to the above-described main peak. Inparticular, it is preferable to have subpeaks with peak tops present atpore radii within the range of 80 nm or more, and 300 nm or less.

In particular, in the case where a main peak with a peak top present ata pore radius of 400 nm or more, and 1,500 nm or less is included, it ispreferable to have subpeaks with peak tops present at pore radii of 300nm or more, and less than 400 nm.

Regarding a pore distribution curve according to the present invention,it is favorable that the pore volume related to the subpeak with a peaktop present at a pore radius of 80 nm or more, and less than 300 nm isusually 0.01 cm³/g or more, preferably 0.02 cm³/g or more, morepreferably 0.03 cm³/g or more, and most preferably 0.04 cm³/g or more,and usually 0.3 cm³/g or less, preferably 0.25 cm³/g or less, morepreferably 0.20 cm³/g or less, and most preferably, 0.18 cm³/g or less.If the upper limit of this range is exceeded, voids between secondarygrains become too much, and in the case where the lithium transitionmetal based compound powder according to the present invention is usedas a positive electrode material, the filling factor of the positiveelectrode active material into a positive electrode plate is reducedand, thereby, the battery capacity may be limited. On the other hand, ifthe pore volume is less than the lower limit of this range, voidsbetween secondary grains become too small and, therefore, in the casewhere a battery is produced while the lithium transition metal basedcompound powder according to the present invention is used as thepositive electrode material, lithium diffusion between secondary grainsis inhibited and the load characteristics may deteriorate.

In the present invention, preferable examples include a lithiumtransition metal based compound powder for a lithium secondary batterypositive electrode material exhibiting the pore distribution curves,based on the mercury penetration method, having at least one main peakwith a peak top present at a pore radius of 300 nm or more, and 1,500 nmor less and having subpeaks with peak tops present at pore radii of 80nm or more, and less than 300 nm.

Furthermore, preferable examples also include a lithium transition metalbased compound powder for a lithium secondary battery positive electrodematerial exhibiting the pore distribution curves, based on the mercurypenetration method, having at least one main peak with a peak toppresent at a pore radius of 400 nm or more, and 1,500 nm or less andhaving subpeaks with peak tops present at pore radii of 300 nm or more,and less than 400 nm.

<Bulk Density>

The bulk density of the lithium transition metal based compound powderaccording to the present invention is usually 1.2 g/cc or more,preferably 1.3 g/cc or more, more preferably 1.4 g/cc or more, and mostpreferably 1.5 g/cc, and usually 2.0 g/cc or less, preferably 1.9 g/ccor less, more preferably 1.8 g/cc or less, and most preferably 1.7 g/ccor less. It is preferable for the powder filling performance and theimprovement in electrode density that the bulk density exceeds thisupper limit. On the other hand, the specific surface area may become toosmall and the battery performance may deteriorate. If the bulk densityis smaller than this lower limit, the powder filling performance and theelectrode preparation may be adversely affected.

In the present invention, the bulk density is determined as a powderpacking density (tap density) g/cc when 5 to 10 g of lithium transitionmetal based compound powder is put into a 10 ml glass graduated cylinderand tapping is conducted 200 times at a stroke of about 20 mm.

<Volume Resistivity>

Regarding the volume resistivity of the lithium transition metal basedcompound powder according to the present invention when compaction isconducted at a pressure of 40 MPa, the lower limit is preferably 1×10³Ω·cm or more, more preferably 1×10⁴ Ω·cm or more, further preferably1×10⁵ Ω·cm or more, and most preferably 5×10⁵ Ω·cm or more. The upperlimit is preferably 1×10⁷ Ω·cm or less, more preferably 8×10⁶ Ω·cm orless, further preferably 5×10⁶ Ω·cm or less, and most preferably 3×10⁶Ω·cm or less. If the volume resistivity exceeds this upper limit, in thecase where a battery is produced, the load characteristics maydeteriorate. On the other hand, if the volume resistivity is less thanthis lower limit, in the case where a battery is produced, the safetyand the like may deteriorate.

In the present invention, the volume resistivity of the lithiumtransition metal based compound powder is a volume resistivity measuredwith a four-probe-ring electrode, where a distance between electrodes is5.0 mm, an electrode radius is 1.0 mm, a sample radius is 12.5 mm, andan applied voltage limiter is set at 90 V, in the state in which alithium transition metal based compound powder is compacted at apressure of 40 MPa. For example, the measurement of the volumeresistivity can be conducted with respect to a powder under apredetermined pressure with a probe unit for a powder by using a powderresistance measuring apparatus (for example, Loresta GP PowderResistivity Measuring System produced by Dia Instruments Co., Ltd.).

<Crystal Structure>

Preferably, the lithium transition metal based compound powder accordingto the present invention contains a lithium nickel manganese cobaltbased composite oxide, which is configured to include a crystalstructure belonging to a layer structure, as a primary component.

Here, the layer structure will be described in further detail. Examplesof typical crystal systems having the layer structure include crystalsystems, such as LiCoO₂ and LiNiO₂, belonging to α-NaFeO₂ type. They arehexagonal systems and belong to a space group

R 3 m  [Mathematical formula 2]

(hereafter may be expressed as a “layer R(−3)m structure) on the basisof the symmetry thereof.

However, layer LiMeO₂ is not limited to the layer R(−3)m structure.Besides this, LiMnO₂, which is so-called layer Mn, is an orthorhombicsystem and is a layer compound of a space group Pm2m. Furthermore,Li₂MnO₃, which is a so-called 213 phase, can be expressed asLi[Li_(1/3)Mn_(2/3)]O₂ and is also a layer compound, in which a Lilayer, a [Li_(1/3)Mn_(2/3)] layer, and an oxygen layer are laminated,although it is a monoclinic system having a space group C2/m structure.

<Composition>

Furthermore, preferably, the lithium-containing transition metalcompound powder according to the present invention is a lithiumtransition metal based compound powder represented by Compositionformula (I) described below.

LiMO₂  (I)

In the formula, M represents elements composed of Li, Ni, and Mn or Li,Ni, Mn, and Co, a Mn/Ni molar ratio is usually 0.1 or more, preferably0.3 or more, more preferably 0.5 or more, further preferably 0.6 ormore, still preferably 0.7 or more, still further preferably 0.8 ormore, and most preferably 0.9 or more, and usually 5 or less, preferably4 or less, more preferably 3 or less, further preferably 2.5 or less,and most preferably 1.5 or less. A Co/(Mn+Ni+Co) molar ratio is usually0 or more, preferably 0.01 or more, more preferably 0.02 or more,further preferably 0.03 or more, and most preferably 0.05 or more, andusually 0.35 or less, preferably 0.20 or less, more preferably 0.15 orless, further preferably 0.10 or less, and most preferably 0.099 orless. A Li molar ratio in M is usually 0.001 or more, preferably 0.01 ormore, more preferably 0.02 or more, further preferably 0.03 or more, andmost preferably 0.05 or more, and usually 0.2 or less, preferably 0.19or less, more preferably 0.18 or less, further preferably 0.17 or less,and most preferably 0.15 or less.

In Composition formula (I) described above, the atomic ratiorepresenting the amount of oxygen is described as 2 for convenience, butsomewhat non-stoichiometry is allowable. In the case where thenon-stoichiometry is present, the atomic ratio of oxygen is within therange of usually 2±0.2, preferably within the range of 2±0.15, morepreferably within the range of 2±0.12, further preferably within therange of 2±0.10, and particularly preferably within the range of 2±0.05.

Preferably, the lithium transition metal based compound powder accordingto the present invention has been fired by conducting high temperaturefiring in an oxygen-containing gas atmosphere in order to enhance thecrystallinity of the positive electrode active material. In particular,regarding the lithium nickel manganese cobalt based composite oxidehaving the composition represented by Composition formula (I) describedabove, the lower limit of the firing temperature is usually 900° C. orhigher, preferably 920° C. or higher, more preferably 940° C. or higher,further preferably 950° C. or higher, and most preferably 960° C. orhigher. The upper limit is 1,200° C. or lower, preferably 1,175° C. orlower, further preferably 1,150° C. or lower, and most preferably 1,125°C. or lower. If the firing temperature is too low, heterogeneous phasesare also present, the crystal structure is not developed, and thelattice strain increases. Furthermore, the specific surface area becomestwo large. Conversely, if the firing temperature is too high, primarygrains grow excessively, sintering between grains proceeds excessively,and the specific surface area becomes too small.

<Carbon Content C>

The value of carbon content C (percent by weight) of the lithiumtransition metal based compound powder according to the presentinvention is usually 0.005 percent by weight or more, preferably 0.01percent by weight or more, further preferably 0.015 percent by weight ormore, and most preferably 0.02 percent by weight or more, and usually0.25 percent by weight or less, preferably 0.2 percent by weight orless, more preferably 0.15 percent by weight or less, further preferably0.1 percent by weight or less, and most preferably 0.07 percent byweight or less. If the carbon content is less than this lower limit, thebattery performance may deteriorate. If the carbon content exceeds theupper limit, in the case where a battery is produced, blistering due togas generation may increase and the battery performance may deteriorate.

In the present invention, the carbon content C of the lithium nickelmanganese cobalt based composite oxide powder is determined throughmeasurement by an infrared absorption method after combustion in anoxygen stream (high frequency furnace type), as shown in an item ofexamples described later.

Incidentally, the carbon content of the lithium nickel manganese cobaltbased composite oxide powder determined through carbon analysisdescribed later can be assumed to indicate information on the amount ofadhesion of carbonate compound, particularly lithium carbonate. This isbecause the value based on the assumption that the entire amount ofcarbon determined through carbon analysis is derived from carbonate ionsalmost agrees with the carbonate ion concentration analyzed through ionchromatography.

On the other hand, in the case where a treatment for combination withelectrically conductive carbon is conducted as a technique to enhanceelectron conductivity, the amount of C exceeding the above-describedspecific range may be detected. However, the C value in the case wheresuch a treatment is conducted is not limited to the above-describedspecific range.

<Favorable Composition>

Regarding the lithium transition metal based composite oxide powder fora lithium secondary battery positive electrode material, it isparticularly preferable that the atomic configuration in the M site ofComposition formula (I) described above is represented by Formula (II)or Formula (II′) described below.

M=Li_(z/(2+z)){(Ni_((1+y)/2)Mn_((1−y)/2))_(1-x)Co_(x)}_(2/(2+z))  (II)

(in Formula (II) described above,

0≦x≦0.1

−0.1≦y≦0.1

(1−x)(0.05−0.98y)≦z≦(1−x)(0.20−0.88y))

M=Li_(z′/(2+z′)){(Ni_((1+y′)/2)Mn_((1−y′)/2))_(1-x′)Co_(x′)}_(2/(2+z′))  (II′)

(in Composition formula (II′),

0.1<x′≦0.35

−0.1≦y′≦0.1

(1−x′)(0.02−0.98y′)≦z′≦(1−x′)(0.20−0.88y′))

In Formula (II) described above, the value of x is usually 0 or more,preferably 0.01 or more, more preferably 0.02 or more, furtherpreferably 0.03 or more, and most preferably 0.04 or more, and usually0.1 or less, preferably 0.099 or less, and most preferably 0.098 orless.

The value of y is usually −0.1 or more, preferably −0.05 or more, morepreferably −0.03 or more, and most preferably −0.02 or more, and usually0.1 or less, preferably 0.05 or less, more preferably 0.03 or less, andmost preferably 0.02 or less.

The value of z is usually (1−x)(0.05−0.98y) or more, preferably(1−x)(0.06−0.98y) or more, more preferably (1−x)(0.07−0.98y) or more,further preferably (1−x)(0.08−0.98y) or more, and most preferably(1−x)(0.10−0.98y) or more, and usually (1−x)(0.20−0.88y) or less,preferably (1−x)(0.18−0.88y) or less, more preferably,(1−x)(0.17−0.88y), and most preferably (1−x)(0.16−0.88y) or less. If zis less than this lower limit, the electrical conductivity deteriorates.If z exceeds the upper limit, deterioration of the performance of thelithium secondary battery by using this may result, for example, theamount of substitution for the transition metal sites increasesexcessively so as to reduce the battery capacity. Furthermore, if z istoo large, the carbon dioxide absorbency of the active material powderincreases and, thereby, carbon dioxide in the air is absorbed easily. Asa result, it is estimated that the carbon content increases.

In Formula (II′) described above, the value of x′ is usually 0.1 ormore, preferably 0.15 or more, more preferably 0.2 or more, furtherpreferably 0.25 or more, and most preferably 0.30 or more, and usually0.35 or less, preferably 0.345 or less, and most preferably 0.34 orless.

The value of y′ is usually −0.1 or more, preferably −0.05 or more, morepreferably −0.03 or more, and most preferably −0.02 or more, and usually0.1 or less, preferably 0.05 or less, more preferably 0.03 or less, andmost preferably 0.02 or less.

The value of z′ is usually (1−x′)(0.02−0.98y′) or more, preferably(1−x′)(0.03−0.98y′) or more, more preferably (1−x′)(0.04−0.98y′) ormore, and most preferably (1−x′)(0.05−0.98y′) or more, and usually(1−x′)(0.20−0.88y′) or less, preferably (1−x′)(0.18−0.88y′) or less,more preferably, (1−x′)(0.17−0.88y′) or less, and most preferably(1−x′)(0.16−0.88y′) or less. If z′ is less than this lower limit, theelectrical conductivity deteriorates. If z′ exceeds the upper limit,deterioration of the performance of the lithium secondary battery byusing this may result, for example, the amount of substitution for thetransition metal sites increases excessively so as to reduce the batterycapacity. Furthermore, if z′ is too large, the carbon dioxide absorbencyof the active material powder increases and, thereby, carbon dioxide inthe air is absorbed easily. As a result, it is estimated that the carboncontent increases.

In the above-described composition range of Formulae (II) and (II′), asz and z′ approach the lower limits, which are stoichiometric, the ratecharacteristic and the output characteristic tend to become low when abattery is produced. Conversely, as z and z′ approach the upper limits,the rate characteristic and the output characteristic tend to becomehigh when a battery is produced, whereas the capacity tends to becomelow. Furthermore, as z and z′ approach the lower limits, that is, amanganese/nickel atomic ratio becomes small, the capacity is ensured ata low charge voltage, whereas the cycle characteristic and the safety ofa battery with the setting of a high charge voltage tend to become low.Conversely, as y and y′ approach the upper limits, the cyclecharacteristic and the safety of a battery with the setting of a highcharge voltage tend to become improved, whereas the discharge capacity,the rate characteristic, and the output characteristic tend to becomelow. Moreover, as x and x′ approach the lower limits, the loadcharacteristics, e.g., the rate characteristic and the outputcharacteristic, tend to become low when a battery is produced.Conversely, as x and x′ approach the higher limits, the ratecharacteristic and the output characteristic tend to become high when abattery is produced. However, if this upper limit is exceeded, in thecase where a high charge voltage is set, the cycle characteristic andthe safety become low and the raw material cost becomes high. It is animportant constituent feature of the present invention to regulate theabove-described composition parameters x, x′, y, y′, z, and z′ withinthe specific range.

Here, a chemical meaning of the Li composition (z, z′ and x, x′) in thelithium nickel manganese cobalt based composite oxide, that is, afavorable composition of the lithium transition metal based compoundpowder according to the present invention, will be described below infurther detail.

As described above, the layer structure is not necessarily limited tothe R(−3)m structure, but it is preferable from the viewpoint ofelectrochemical performance that the layer structure can belong to theR(−3)m structure.

The above-described x, x′, y, y′, z, and z′ of the composition formulaof the lithium transition metal based compound are determined throughcalculation by analyzing individual transition metals and Li with aninductively coupled plasma atomic emission spectroscope (ICP-AES) anddetermining the ratio of Li/Ni/Mn/Co.

From the structural viewpoint, it is believed that Li related to z andz′ is introduced in the same transition metal site by substitution.Here, according to Li related to z and z′, the average valence of Nibecomes larger than divalent (trivalent Ni is generated) on the basis ofa principle of charge neutrality. Since z and z′ increase the averagevalence of Ni, they serve as indices of the valence of Ni (proportion ofNi(III)).

When the valence (m) of Ni along with changes in z and z′ is calculatedfrom Composition formulae described above,

[Mathematical  formula  3]$m = {2\left\lbrack {2 - \frac{1 - x - z}{\left( {1 - x} \right)\mspace{14mu} \left( {1 + y} \right)}} \right\rbrack}$$m = {2\left\lbrack {2 - \frac{1 - x^{\prime} - z^{\prime}}{\left( {1 - x^{\prime}} \right)\mspace{14mu} \left( {1 + y^{\prime}} \right)}} \right\rbrack}$

are derived on the assumption that the valence of Co is trivalent andthe valence of Mn is tetravalent. This calculation result indicates thatthe valence of Ni is not determined on the basis of merely z and z′, butis a function of x, x′ and y, y′. When z, z′=0 and y, y′=0, the valenceof Ni remains divalent regardless of the values of x, x′. In the casewhere z, z′ become negative values, it is indicated that the amount ofLi contained in the active material is less than a stoichiometricamount, and as for a too large negative value, the effects of thepresent invention may not be exerted. On the other hand, it is indicatedthat even when the z, z′ values are equal, the Ni-rich (y, y′ values arelarge) and/or Co-rich (x, x′ values are large) composition exhibitshigher valence of Ni. As a result, in the case where such a compositionis used for a battery, the rate characteristic and the outputcharacteristic become high, whereas the capacity is reduced easily.Consequently, it can be said more preferable that the upper limit andthe lower limit of z, z′ values are specified as functions of x, x′ andy, y′.

Furthermore, in the case where the x value is within the range of0≦x≦0.1 in which the amount of Co is small, the cost is reduced and, inaddition, in the use as a lithium secondary battery designed to becharged at a high charge potential, the charge-discharge capacity, thecycle characteristic, and the safety are improved.

On the other hand, in the case where the x′ value is within the range of0.10≦x′≦0.35 in which the amount of Co is relatively large, in the useas a lithium secondary battery, the charge-discharge capacity, the cyclecharacteristic, the load characteristics, and the safety are improved ina balanced manner.

<Powder X-Ray Diffraction Peak>

In the present invention, the lithium nickel manganese cobalt basedcomposite oxide powder having a composition satisfying Compositionformulae (I) and (II) described above is characterized in that in thepowder X-ray diffraction pattern by using CuKα rays, when the full widthat half maximum of a (110) diffraction peak present at a diffractionangle 2θ in the vicinity of 64.5° is assumed to be FWHM(110), theFWHM(110) is within the range of 0.01≦FWHM(110)≦0.3.

In general, the full width at half maximum of an X-ray diffraction peakis used as a yardstick to measure the crystallinity. Therefore, thepresent inventors conducted intensive research on the interrelationbetween the crystallinity and the battery performance. As a result, itwas found that good battery performance was exhibit in the case wherethe value of the full width at half maximum of a (110) diffraction peakpresent at a diffraction angle 2θ in the vicinity of 64.5° was within aspecific range.

In the present invention, FWHM(110) is usually 0.01 or more, preferably0.05 or more, more preferably 0.10 or more, further preferably 0.12 ormore, and most preferably 0.14 or more, and usually 0.3 or less,preferably 0.28 or less, more preferably 0.26 or less, furtherpreferably 0.24 or less, and most preferably 0.22 or less.

Furthermore, in the present invention, in powder X-ray diffractometry byusing CuKα rays of the lithium nickel manganese cobalt based compositeoxide powder having a composition satisfying Composition formulae (I)and (II) described above, it is preferable that regarding a (018)diffraction peak present at a diffraction angle 2θ in the vicinity of64°, a (110) diffraction peak present in the vicinity of 64.5°, and a(113) diffraction peak present in the vicinity of 68°, no diffractionpeak originated from a heterogeneous phase is present on the side at anangle higher than the angle of each peak top, or in the case wherediffraction peaks originated from heterogeneous phases are present, theratio of the integrated intensity of heterogeneous phase peaks to thatof the diffraction peak of each intrinsic crystal phase is within thefollowing range.

0≦I ₀₁₈ */I ₀₁₈≦0.20

0≦I ₁₁₀ */I ₁₁₀≦0.25

0≦I ₁₁₃ */I ₁₁₃≦0.30

(Here, I₀₁₈, I₀₁₈, and I₁₁₃ represent integrated intensities of the(018), (110), and (113) diffraction peaks, respectively, and I₀₁₈*,I₁₁₀*, and I₁₁₃* represent integrated intensities of the diffractionpeaks originated from heterogeneous phases and observed on the sides atangles higher than the angles of peak tops of the (018), (110), and(113) diffraction peaks, respectively.)

Incidentally, the details of a causative substance of the diffractionpeak originated from this heterogeneous phase is not certain, and if theheterogeneous phase is included, the rate characteristic, the cyclecharacteristic, and the like deteriorate when a battery is produced.Consequently, the diffraction peaks may include diffraction peaks to theextent that does not adversary affect the battery performance accordingto the present invention. However, it is preferable that the proportionis within the above-described range. The ratio of the integratedintensity of diffraction peaks originated from heterogeneous phases tothat of each diffraction peak is usually I₀₁₈*/I₀₁₈≦0.20,I₁₁₀*/I₁₁₀≦0.25, and I₁₁₃*/I₁₁₃≦0.30, preferably I₀₁₈*/I₀₁₈≦0.15,I₁₁₀*/I₁₁₀≦0.20, and I₁₁₃*/I₁₁₃≦0.25, more preferably I₀₁₈*/I₀₁₈≦0.10,I₁₁₀*/I₁₁₀≦0.15, I₁₁₃*/I₁₁₃≦0.20, further preferably I₀₁₈*/I₀₁₈≦0.05,I₁₁₀*/I₁₁₀≦0.10, I₁₁₃*/I₁₁₃≦0.15, and most preferably, there is nodiffraction peak originated from the heterogeneous phase.

<Reason that Lithium Transition Metal Based Compound Powder According tothe Present Invention Exerts the Above-Described Effects>

The reason that lithium transition metal based compound powder accordingto the present invention exerts the above-described effects is believedas described below.

That is, it is estimated as follows. Regarding the lithium transitionmetal based compound powder according to the present invention,crystalline secondary grains maintain spherical skeletons, the amount ofmercury penetration during pressurization in a mercury penetration curveis large, and pore volumes between crystal grains are large.

Therefore, in the case where a battery is produced by using this, it ispossible to increase the contact area between the positive electrodeactive material surface and an electrolytic solution. In addition, thesurface state becomes suitable for improving the load characteristics(in particular, low-temperature output characteristic), thecrystallinity is developed to a high extent, and furthermore, the ratioof presence of heterogeneous phase is reduced to a very low level. As aresult, excellent balance in characteristics and excellent powderhandleability required for the positive electrode active material can beachieved.

<Method for Manufacturing Lithium Transition Metal Based Compound Powderfor Lithium Secondary Battery Positive Electrode Material>

A method for manufacturing the lithium transition metal based compoundpowder according to the present invention is not limited to a specificmanufacturing method. Production is conducted favorably by a method formanufacturing a lithium transition metal based compound powder for alithium secondary battery positive electrode material according to thepresent invention including the steps of pulverizing a lithium compound,at least one type of transition metal compound selected from V, Cr, Mn,Fe, Co, Ni, and Cu, Additive 1, and Additive 2 in a liquid medium andpreparing a slurry in which they are dispersed homogeneously in a slurrypreparation step, spray-drying the resulting slurry in a spray-dryingstep, and firing the resulting spray-dried substance in a firing step.

For example, an explanation will be made with reference to a lithiumnickel manganese cobalt based composite oxide powder. A slurry in whicha lithium compound, a nickel compound, a manganese compound, a cobaltcompound, Additive 1, and Additive 2 are dispersed in a liquid medium isspray-dried, and the resulting spray-dried substance is fired in anoxygen-containing gas atmosphere, so that the production can beconducted.

The method for manufacturing a lithium transition metal based compoundpowder according to the present invention will be described below indetail with reference to the method for manufacturing a lithium nickelmanganese cobalt based composite oxide powder which is a favorable formof the present invention.

<Slurry Preparation Step>

In production of a lithium transition metal based compound powder by amethod according to the present invention, among raw material compoundsused for preparation of a slurry, examples of lithium compounds includeLi₂CO₃, LiNO₃, LiNO₂, LiOH, LiOH.H₂O, LiH, LiF, LiCl, LiBr, LiI,CH₃OOLi, Li₂O, Li₂SO₄, Li dicarboxylate, Li citrate, fatty acid lithium,and alkyllithium. Among these lithium compounds, lithium compounds whichdo not contain a nitrogen atom, a sulfur atom, nor a halogen atom arepreferable because harmful substances, e.g., SO_(x) and NO_(x), are notgenerated during a firing treatment. Furthermore, compounds in whichvoids are formed easily through, for example, generation ofdecomposition gases during firing and generation of decomposition gasesin secondary grains of spray-dried powder, are preferable. Inconsideration of these points, Li₂CO₃, LiOH, and LiOH.H₂O arepreferable, and in particular Li₂CO₃ is preferable. One type of theselithium compounds may be used alone or at least two types may be used incombination.

Examples of nickel compounds include Ni(OH)₂, NiO, NiOOH, NiCO₃,2NiCO₃.3Ni(OH)₂4H₂O, NiC₂O₄.2H₂O, Ni(NO₃)₂.6H₂O, NiSO₄.6H₂O, fatty acidnickel, and nickel halide. Among them, nickel compounds, such asNi(OH)₂, NiO, NiOOH, NiCO₃, 2NiCO₃.3Ni(OH)₂.4H₂O, and NiC₂O₄.2H₂O arepreferable because harmful substances, e.g., SO_(x) and NO_(x), are notgenerated during a firing treatment. Furthermore, Ni(OH)₂, NiO, NiOOH,and NiCO₃ are preferable from the viewpoint of availability asinexpensive industrial raw materials and from the viewpoint of highreactivity. Moreover, Ni(OH)₂, NiOOH, and NiCO₃ are particularlypreferable from the viewpoint that voids are formed in secondary grainsof spray-dried powder easily through, for example, generation ofdecomposition gases during firing. One type of these nickel compoundsmay be used alone or at least two types may be used in combination.

Examples of manganese compounds include manganese oxides, e.g., Mn₂O₃,MnO₂, and Mn₃O₄, manganese salts, e.g., MnCO₃, Mn(NO₃)₂, MnSO₄,manganese acetate, manganese dicarboxylate, manganese citrate, and fattyacid manganese, oxyhydroxides, and halides, e.g., manganese chloride.Among these manganese compounds, MnO₂, Mn₂O₃, Mn₃O₄, and MnCO₃ arepreferable because gases, e.g., SO_(x) and NO_(x), are not generatedduring a firing treatment and, furthermore, there is ease ofavailability as inexpensive industrial raw materials. One type of thesemanganese compounds may be used alone or at least two types may be usedin combination.

Examples of cobalt compounds include Co(OH)₂, CoOOH, CoO, Co₂O₃, Co₃O₄,Co(OCOCH₃)₂.4H₂O, CoCl₂, Co(NO₃)₂.6H₂O, Co(SO₄)₂.7H₂O, and CoCO₃. Mostof all, Co(OH)₂, CoOOH, CoO, Co₂O₃, Co₃O₄, and COCO₃ are preferablebecause harmful substances, e.g., SO_(x) and NO_(x), are not generatedduring a firing treatment, and Co(OH)₂ and CoOOH are further preferablefrom the viewpoint of industrial availability at low prices and highreactivity. In addition, Co(OH)₂, CoOOH, and CoCO₃ are particularlypreferable from the viewpoint that voids are formed in secondary grainsof spray-dried powder easily through, for example, generation ofdecomposition gases during firing. One type of these cobalt compoundsmay be used alone or at least two types may be used in combination.

Besides the above-described Li, Ni, Mn, and Co raw material compounds,it is possible to use a group of compounds for the purpose ofintroducing the above-described foreign elements by conductingsubstitution with the foreign elements and forming voids efficiently insecondary grains formed by spray-drying described later. The stage ofaddition of the compounds used here for the purpose of forming voidsefficiently in secondary grains can be selected from one of beforemixing of raw materials and after the mixing depending on the propertiesthereof. In particular, it is preferable that compounds which aredecomposed easily by, for example, application of a mechanical shearstress because of a mixing step are added after the mixing step.

Additive 1 is as described above. Furthermore, Additive 2 is asdescribed above.

A method for mixing the raw materials is not specifically limited andmay be either a wet type or a dry type. Examples thereof include methodsin which apparatuses, e.g., a ball mill, a vibration mill, and a beadsmill, are used. The wet mixing, in which raw material compounds aremixed in a liquid medium, e.g., water or alcohol, is preferable becausemore homogeneous mixing can be conducted and, in addition, thereactivity of the mixture can be enhanced in a firing step.

The mixing time is different depending on the mixing method. However, itis enough that the raw materials are mixed homogeneously at a grainlevel. For example, as for the ball mill (wet type or dry type), themixing time is usually about 1 hour to 2 days, and as for the beads mill(continuous wet method), the residence time is usually about 0.1 hour to6 hours.

Incidentally, at the mixing stage of the raw materials, it is preferablethat pulverization of the raw materials is conducted in combination withthe mixing. Regarding the degree of pulverization, the grain sizes ofthe raw material grains after the pulverization serve as indices, andthe average grain size (median size) is specified to be usually 0.4 μmor less, preferably 0.3 μm or less, further preferably 0.25 μm or less,and most preferably 0.2 μm or less. If the average grain size of the rawmaterial grains after the pulverization is too large, the reactivity inthe firing step deteriorates and, in addition, the composition does notbecome uniform easily. However, excessive reduction in grain size leadsto an increase in pulverization cost. Therefore, it is enough thatpulverization is conducted in such a way as to control the average grainsize at usually 0.01 μm or more, preferably 0.02 μm or more, and furtherpreferably 0.05 μm or more. Means for realizing such a degree ofpulverization is not specifically limited, but a wet pulverizationmethod is preferable. Specific examples thereof include DYNO-MILL.

In the present invention, the median size of pulverized grains in theslurry is measured with a known laser diffraction/scattering grain sizedistribution measuring apparatus, where the refractive index is set at1.24 and the reference of grain size is set to be on a volume basis. Inthe present invention, a 0.1 percent by weight sodium hexametaphosphateaqueous solution was used as a dispersion medium used in a measurementand the measurement was conducted after 5 minutes of ultrasonicdispersion (output 30 W, frequency 22.5 kHz). The median sizes ofspray-dried substance described later were measured under the samecondition except that the measurement were conducted after 0, 1, 3, and5 minutes of ultrasonic dispersion, respectively.

<Spray-Drying Step>

After the wet mixing, usually, a drying step is conducted. The dryingmethod is not specifically limited, but spray drying is preferable fromthe viewpoint of homogeneity and powder fluidity of the resultinggrained substances, powder handleability, efficient production of driedgrains, and the like.

<Spray-Dried Powder>

In the method for manufacturing a lithium transition metal basedcompound powder, e.g., the lithium nickel manganese cobalt basedcomposite oxide powder, according to the present invention, the slurryobtained by wet-pulverizing the raw material compounds, Additive 1, andAdditive 2 is spray-dried and, thereby, a powder in which primary grainsare aggregated so as to form secondary grains is obtained. Thespray-dried powder in which primary grains are aggregated so as to formsecondary grains is a characteristic shape of the spray-dried powderaccording to the present invention. Examples of methods for identifyingthe shape include SEM observation and cross-sectional SEM observation.

The median size (here, the value measured without applying ultrasonicdispersion) of the powder obtained by spray-drying, which is a firingprecursor of the lithium transition metal based compound powder, e.g.,the lithium nickel manganese cobalt based composite oxide powder,according to the present invention is specified to be usually 10 μm orless, more preferably 9 μm or less, further preferably 8 μm or less, andmost preferably 7 μm or less. However, extremely small grain size tendsto be difficult to obtain and, therefore, the median size is usually 3μm or more, preferably 4 μm or more, and more preferably 5 μm or more.In the case where grained substances are produced by the spray-dryingmethod, the grain sizes thereof can be controlled by selecting thespraying type, the pressuring gas stream supply rate, the slurry supplyrate, the drying temperature, and the like appropriately.

That is, in the production of the lithium nickel manganese cobalt basedcomposite oxide powder by spray-drying the slurry in which, for example,a lithium compound, a nickel compound, a manganese compound, a cobaltcompound, Additive 1, and Additive 2 are dispersed in a liquid mediumand, thereafter, firing the resulting powder, spray drying is conductedunder a condition in which the slurry viscosity V satisfies 50cp≦V≦4,000 cp and the gas liquid ratio G/S satisfies 500≦G/S≦10,000,where V (cp) represents a slurry viscosity, S (L/min) represents anamount of supply of slurry, and G (L/min) represents an amount of supplyof gas in the spray drying.

If the slurry viscosity V (cp) is too low, the powder in which primarygrains are aggregated so as to form secondary grains may becomedifficult to obtain. If the slurry viscosity is too high, a feed pumpmay go out of order or a nozzle may be clogged. Therefore, regarding theslurry viscosity V (cp), the lower limit value is usually 50 cp or more,preferably 100 cp or more, further preferably 300 cp or more, and mostpreferably 500 cp, and the upper limit is usually 4,000 cp or less,preferably 3,500 cp or less, further preferably 3,000 cp or less, andmost preferably 2,500 cp or less.

If the gas liquid ratio G/S is smaller than the above-described lowerlimit, for example, the secondary grain size may become coarse, and thedrying performance may deteriorate. If the upper limit is exceeded, theproductivity may deteriorate. Therefore, regarding the gas liquid ratioG/S, the lower limit is usually 500 or more, preferably 800 or more,further preferably 1,000 or more, and most preferably 1,500 or more. Theupper limit is usually 10,000 or less, preferably 9,000 or less, furtherpreferably 8,000 or less, and most preferably 7,500 or less.

The amount S of supply of slurry and the amount G of supply of gas areset appropriately on the basis of the viscosity of slurry subjected tospray drying, specifications of a spray-drying apparatus to be used, andthe like.

In the method of the present invention, it is enough that the spraydrying is conducted while the above-described slurry viscosity V (cp) issatisfied and the amount of supply of slurry and the amount of supply ofgas suitable for the specification of the spray-drying apparatus to beused are controlled so as to satisfy the above-described range of gasliquid ratio G/S. The other conditions are set appropriately inaccordance with the type of the apparatus to be used and the like and itis preferable that the following conditions are selected.

That is, it is favorable that the spray drying of the slurry isconducted at usually 50° C. or higher, preferably 70° C. or higher,further preferably 120° C. or higher, and most preferably 140° C. orhigher, and usually 300° C. or lower, preferably 250° C. or lower,further preferably 200° C. or lower, and most preferably 180° C. orlower. If this temperature is too high, there is a possibility that mostof the resulting granulated grains have a hollow structure and thepacking density of the powder may be reduced. On the other hand, if thetemperature is too low, powder adhesion-clogging problems and the likedue to dew condensation at a powder outlet portion may occur.

Furthermore, the spray-dried powder of the lithium transition metalbased compound powder, e.g., the lithium nickel manganese cobalt basedcomposite oxide powder, according to the present invention ischaracterized in that the cohesive force between primary grains issmall. This can be ascertained by examining changes in median size alongwith the ultrasonic dispersion. Here, the upper limit of the median sizeof the spray-dried grains measured after being subjected to 5 minutes ofultrasonic dispersion “Ultra Sonic” (output 30 W, frequency 22.5 kHz) isusually 4 μm or less, preferably 3.5 μm or less, more preferably 3 μm orless, further preferably 2.5 μm or less, and most preferably 2 μm orless. The lower limit is usually 0.01 μm or more, preferably 0.05 μm ormore, more preferably 0.1 μm or more, and most preferably 0.2 μm ormore. Regarding a lithium transition metal based compound powder firedby using the spray-dried grains having a median size after theultrasonic dispersion larger than the above-described value, voidsbetween grains are small and the load characteristics are not improved.On the other hand, regarding a lithium transition metal based compoundpowder fired by using the spray-dried grains having a median size afterthe ultrasonic dispersion smaller than the above-described value, voidsbetween grains become too large and problems may occur in that the bulkdensity is reduced, the coating performance deteriorates, and the like.

The bulk density of the spray-dried grains of the lithium transitionmetal based compound powder, e.g., the lithium nickel manganese cobaltbased composite oxide powder, according to the present invention isusually 0.1 g/cc or more, preferably 0.3 g/cc or more, more preferably0.5 g/cc or more, and most preferably 0.7 g/cc or more. If the bulkdensity is lower than this lower limit, the powder filling performanceand the powder handleability may be adversely affected. Furthermore, thebulk density is usually 1.7 g/cc or less, preferably 1.6 g/cc or less,more preferably 1.5 g/cc or less, and most preferably 1.4 g/cc or less.It is preferable for the powder filling performance and the powderhandleability that the bulk density exceeds the upper limit, whereas thespecific surface area may become too small and the reactivity in thefiring step may deteriorate.

If the specific surface area is small, the reactivity of the powder,which is obtained by the spray drying, with the lithium compound isreduced in the firing reaction, which is the next step, with the lithiumcompound. Therefore, as described above, it is preferable that thespecific surface area is maximized by the means, e.g., pulverization ofthe raw material before spray drying. On the other hand, an excessiveincrease in specific surface area is industrially disadvantageous and,in addition, the lithium transition metal based compound according tothe present invention may not be obtained. Consequently, the BETspecific surface area of the thus obtained spray-dried grains isspecified to be usually 10 m²/g or more, preferably 20 m²/g or more,further preferably 30 m²/g or more, and most preferably 50 m²/g or more,and usually 100 m²/g or less, preferably 80 m²/g or less, furtherpreferably 70 m²/g or less, and most preferably 65 m²/g or less.

<Firing Step>

The thus obtained firing precursor is then subjected to a firingtreatment.

Here, in the present invention, the “firing precursor” refers to aprecursor of the lithium transition metal based compound, e.g., thelithium nickel manganese cobalt based composite oxide, before firing,the precursor being obtained by treating the spray-dried grains. Forexample, the above-described compound which generates decompositiongases or sublimates during the firing to form voids in secondary grainsmay be contained in the above-described spray-dried grains so as to formthe firing precursor.

This firing condition is depending on the composition and lithiumcompound raw material used. However, the tendency is as described below.If the firing temperature is too high, primary grains grow excessively,sintering between grains proceeds excessively, and the specific surfacearea becomes too small. Conversely, if the firing temperature is toolow, heterogeneous phases are present together, the crystal structure isnot developed, and the lattice strain increases. Furthermore, thespecific surface area becomes two large. The firing temperature isusually 700° C. or higher. However, regarding the compositionrepresented by General formulae (I) and (II) described above, the firingtemperature is preferably 900° C. or higher, more preferably 920° C. orhigher, further preferably 940° C. or higher, still preferably 950° C.or higher, and most preferably 960° C. or higher, and usually 1,200° C.or lower, preferably 1,175° C. or lower, further preferably 1,150° C. orlower, and most preferably 1,125° C. or lower.

As for firing, for example, a box furnace, a tube furnace, a tunnelfurnace, a rotary kiln, and the like can be used. Usually, the firingstep can be divided into three parts of temperature raising-maximumtemperature keeping temperature lowering. The second part of maximumtemperature keeping is not necessarily once, and may include two or morestages depending on the purpose. The steps of temperatureraising-maximum temperature keeping-temperature lowering may be repeatedtwice or more times while a disintegration step referring to eliminateagglomeration in such a way that secondary grains are not broken or apulverization step referring to crush until primary grains or a stillfiner powder results is conducted therebetween.

Regarding the temperature raising step, the temperature in the furnaceis raised at a temperature increase rate of usually 1° C./min or more,and 10° C./min or less. If this temperature increase rate is too low, ittakes much time and, therefore, it is industrially disadvantageous.However, if the temperature increase rate is too high, the temperaturein the furnace do not follow the set temperature depending on furnaces.The temperature increase rate is preferably 2° C./min or more, morepreferably 3° C./min or more, and preferably 7° C./min or less, and morepreferably 5° C./min or less.

The keeping time in the maximum temperature keeping step is differentdepending on the temperature. However, in the above-describedtemperature range, the keeping time is usually 30 minutes or more,preferably 1 hour or more, further preferably 3 hours or more, and mostpreferably 5 hours or more, and 50 hours or less, preferably 25 hours orless, further preferably 20 hours or less, and most preferably 15 hoursor less. If the firing time is too short, a lithium transition metalbased compound powder exhibiting good crystallinity is not obtainedeasily, and a too long firing time is not practical. A too long firingtime is disadvantageous because disintegration may become necessarythereafter, or pulverization may become difficult.

In the temperature lowering step, the temperature in the furnace islowered at a temperature decrease rate of usually 0.1° C./min or more,and 10° C./min or less. If this temperature decrease rate is too low, ittakes much time and, therefore, it is industrially disadvantageous.However, if the temperature decrease rate is too high, the homogeneityof an object tends to become poor, and deterioration of a containertends to be accelerated. The temperature decrease rate is preferably 1°C./min or more, more preferably 3° C./min or more, and preferably 7°C./min or less, and more preferably 5° C./min or less.

Regarding the atmosphere in the firing, since there is an oxygen partialpressure region suitable for the composition of the lithium transitionmetal based compound powder to be produced, various gas atmospheressuitable for satisfying them are used. Examples of gas atmospheres caninclude oxygen, air, nitrogen, argon, hydrogen, carbon dioxide, andmixed gases thereof. Regarding the lithium nickel manganese cobalt basedcomposite oxide powder specifically conducted in the present invention,oxygen-containing gas atmospheres, e.g., air, can be used. The oxygenconcentration in the atmosphere is usually 1 percent by volume or more,preferably 10 percent by volume or more, and more preferably 15 percentby volume or more, and 100 percent by volume or less, preferably 50percent by volume or less, and more preferably 25 percent by volume orless.

Regarding the above-described manufacturing method, in the case wherethe lithium transition metal based compound powder, e.g., the lithiumnickel manganese cobalt based composite oxide powder having theabove-described specific composition, according to the present inventionis produced, when the manufacturing condition is constant, the desiredLi/Ni/Mn/Co molar ratio can be controlled by adjusting the mixing ratioof individual compounds in the preparation of the slurry in which thelithium compound, the nickel compound, the manganese compound, thecobalt compound, Additive 1, and Additive 2 are dispersed in the liquidmedium.

According to the thus obtained lithium transition metal based compoundpowder, e.g., the lithium nickel manganese cobalt based composite oxidepowder, of the present invention, a lithium secondary battery positiveelectrode material having a high capacity, exhibiting excellentlow-temperature output characteristic and preservation characteristic,and exhibiting good performance balance is provided.

[Lithium Secondary Battery Positive Electrode]

A lithium secondary battery positive electrode according to the presentinvention is produced by forming a positive electrode active materiallayer containing the lithium transition metal based compound powder fora lithium secondary battery positive electrode material according to thepresent invention and a binder on a collector.

Usually, the positive electrode active material layer is formed bycontact bonding a sheet-shaped mixture, in which a positive electrodematerial, a binder, if necessary an electrically conductive material anda thickener, and the like are dry-mixed, to a positive electrodecollector or dissolving or dispersing these materials into a liquidmedium to prepare a slurry, applying the slurry to a positive electrodecollector, and conducting drying.

As for a material for the positive electrode collector, usually, metalmaterials, e.g., aluminum, stainless steel, nickel plating, titanium,and tantalum, and carbon materials, e.g., carbon cloth and carbon paper,are used. Most of all, metal materials are preferable, and aluminum isparticularly preferable. Examples of shapes of metal materials includemetal foil, metal cylindrical columns, metal coils, metal sheets, metalthin films, expanded metals, punched metals, and foam metals. Examplesof shapes of carbon materials include carbon sheets, carbon thin films,and carbon cylindrical columns. Most of all, metal thin films arepreferable because they are used for industrial products at present. Thethin film may be formed into a mesh appropriately.

In the case where the thin film is used as the positive electrodecollector, the thickness thereof is optional. However, favorablethickness is within the range of usually 1 μm or more, preferably 3 μmor more, more preferably 5 μm or more, and usually 100 mm or less,preferably 1 mm or less, and more preferably 50 μm or less. If thethickness is smaller than the above-described range, the structurerequired for a collector may become insufficient. On the other hand, ifthe thickness is larger than the above-described range, thehandleability may be impaired.

The binder used for producing the positive electrode active materiallayer is not specifically limited. As for a coating method, it is enoughthat the material is stable toward a liquid medium used in electrodeproduction. Specific examples thereof include resin polymers, e.g.,polyethylenes, polypropylenes, polyethylene terephthalates, polymethylmethacrylates, aromatic polyamides, celluloses, and nitrocelluloses;rubber polymers, e.g., SBR (styrene-butadiene rubber, NBR(acrylonitrile-butadiene rubber), fluororubber, isoprene rubber,butadiene rubber, and ethylene-propylene rubber; thermoplastic elastomerpolymers, e.g., styrene-butadiene-styrene block copolymers andhydrogenated products thereof, EPDM (ethylene-propylene-diene ternarypolymer), styrene-ethylene-butadiene-ethylene copolymers, andstyrene-isoprene-styrene block copolymers and hydrogenated productsthereof; soft resin polymers, e.g., syndiotactic-1,2-polybutadiene,polyvinyl acetates, ethylene-vinyl acetate copolymers, andpropylene-α-olefin copolymers; fluoropolymers, e.g., polyvinylidenefluorides, polytetrafluoroethylenes, fluorinated polyvinylidenefluorides, and polytetrafluoroethylene-ethylene copolymers; and polymercompositions having ionic conductivity of alkali metal ions(particularly lithium ion). One type of these substances may be usedalone or at least two types may be used together in any combination atany ratio.

The proportion of the binder in the positive electrode active materiallayer is usually 0.1 percent by weight or more, preferably 1 percent byweight or more, and further preferably 5 percent by weight or more, andusually 80 percent by weight or less, preferably 60 percent by weight orless, further preferably 40 percent by weight or less, and mostpreferably 10 percent by weight or less. If the proportion of the binderis too low, there is a possibility that the positive electrode activematerial cannot be held sufficiently, the mechanical strength of thepositive electrode becomes insufficient, and the battery performance,e.g., a cycle characteristic, deteriorates. On the other hand, a toohigh proportion may lead to reduction in the battery capacity and theelectrical conductivity.

The positive electrode active material is usually allowed to contain anelectrically conductive material in order to increase the electricalconductivity. The type thereof is not specifically limited. Specificexamples thereof can include metal materials, e.g., copper and nickel,and carbon materials, for example, graphite, e.g., natural graphite andartificial graphite; carbon black, e.g., acetylene black; and amorphouscarbon, e.g., needle coke. One type of these substances may be usedalone or at least two types may be used together in any combination atany ratio. The proportion of the electrically conductive material in thepositive electrode active material layer is usually 0.01 percent byweight or more, preferably 0.1 percent by weight or more, and furtherpreferably 1 percent by weight or more, and usually 50 percent by weightor less, preferably 30 percent by weight or less, and further preferably20 percent by weight or less. If the proportion of the electricallyconductive material is too low, the electrical conductivity may becomeinsufficient. Conversely, if the proportion is too high, the batterycapacity may be reduced.

The type of liquid medium for forming the slurry is not specificallylimited insofar as it is a solvent capable of dissolving or dispersingthe lithium transition metal based compound powder, which is thepositive electrode material, the binder, and the electrically conductivematerial and the thickener, which are used as necessary, and either anaqueous solvent or an organic solvent may be used. Examples of aqueoussolvents include water and alcohol. Examples of organic solvents caninclude N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide,methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate,diethyltriamine, N,N-dimethylaminopropylamine, ethylene oxide,tetrahydrofuran (THF), toluene, acetone, dimethyl ether,dimethylacetamide, hexamethylphosphoramide, dimethylsulfoxide, benzene,xylene, quinoline, pyridine, methylnaphthalene, and hexane. Inparticular, in the case where the aqueous solvent is used, a dispersantis added besides the thickener, and slurry is prepared by using latex,e.g., SBR. One type of these solvents may be used alone or at least twotypes may be used together in any combination at any ratio.

The content of the lithium transition metal based compound powderaccording to the present invention serving as the positive electrodematerial in the positive electrode active material layer is usually 10percent by weight or more, preferably 30 percent by weight or more, andfurther preferably 50 percent by weight or more, and usually 99.9percent by weight or less, and preferably 99 percent by weight or less.If the proportion of the lithium transition metal based compound powderin the positive electrode active material layer is too large, thestrength of the positive electrode tends to become insufficient. If theproportion is too small, the capacity may become insufficient.

The thickness of the positive electrode active material layer is usuallyabout 10 to 200 μm.

Preferably, the positive electrode active material layer obtained bycoating and drying is compacted through roller press or the like inorder to increase the packing density of the positive electrode activematerial.

In this manner, the lithium secondary battery positive electrodeaccording to the present invention can be prepared.

<Lithium Secondary Battery>

A lithium secondary battery according to the present invention includesthe above-described positive electrode capable of absorbing andreleasing lithium, according to the present invention, a negativeelectrode capable of absorbing and releasing lithium, and a non-aqueouselectrolyte containing a lithium salt serving as an electrolytic salt.Furthermore, a separator for holding the non-aqueous electrolyte may beprovided between the positive electrode and the negative electrode. Itis desirable to interpose the separator, as described above, in order toeffectively prevent an occurrence of short-circuit due to contactbetween the positive electrode and the negative electrode.

<Negative Electrode>

Usually, the negative electrode is constructed by forming a negativeelectrode active material layer on a negative electrode collector, as inthe positive electrode.

As for a material for the negative electrode collector, metal materials,e.g., copper, nickel, stainless steel, and nickel plated steel, andcarbon materials, e.g., carbon cloth and carbon paper, are used. Most ofall, regarding the metal materials, metal foil, metal cylindricalcolumns, metal coils, metal sheets, metal thin films, and the like arementioned. Regarding the carbon materials, carbon sheets, carbon thinfilms, carbon cylindrical columns, and the like are mentioned. Most ofall, metal thin films are preferable because they are used forindustrial products at present. The thin film may be formed into a meshappropriately. In the case where the thin film is used as the negativeelectrode collector, the range of favorable thickness thereof is equalto the above-described range with respect to the positive electrodecollector.

The negative electrode active material layer is configured to contain anegative electrode active material. The type of the negative electrodeactive material is not specifically limited insofar as it can absorb andrelease lithium ions electrochemically. However, usually, the carbonmaterials capable of absorbing and releasing lithium ions are used fromthe viewpoint of a high degree of safety.

The type of the carbon material is not specifically limited. Examplesthereof include graphite, e.g., artificial graphite and naturalgraphite, and thermal decomposition products of organic materials undervarious thermal decomposition conditions. Examples of thermaldecomposition products of organic materials include coal based coke,petroleum based coke, carbonized products of coal based pitch,carbonized products of petroleum based pitch, carbonized products ofthese pitches subjected to an oxidation treatment, needle coke, pitchcoke, carbonized products of, for example, phenol resins and crystallinecelluloses, and the like, carbon materials prepared by graphitizing apart of them, furnace black, acetylene black, and pitch based carbonfibers. Among them, graphite is preferable. Particularly favorably,artificial graphite, refined natural graphite, which are produced bysubjecting graphitizable pitches obtained from various raw materials toa high temperature heat treatment, graphite materials in which a pitchis included in the above-described graphite, and the like are mainlyused after being subjected to various surface treatments. One type ofthese carbon materials may be used alone or at least two types may beused in combination.

In the case where a graphite material is used as the negative electrodeactive material, it is favorable that the d value (interlayer distance:d₀₀₂) of the lattice plane (002 plane) determined through X-raydiffraction based on Gakushin method is usually 0.335 nm or more,usually 0.34 nm or less, and preferably 0.337 nm or less.

The ash content of the graphite material is usually 1 percent by weightor less relative to the weight of the graphite material, and most ofall, 0.5 percent by weight or less, in particular 0.1 percent by weightor less is preferable.

Furthermore, the crystallite size (Lc) of the graphite material,determined through X-ray diffraction based on Gakushin method, isusually 30 nm or more. Most of all, 50 nm or more, and in particular 100nm or more is preferable.

Preferably, the median size of the graphite material, determined by alaser diffraction scattering method, is usually 1 μm or more, most ofall 3 μm or more, furthermore 5 μm or more, and in particular 7 μm ormore, and usually 100 μm or less, most of all, 50 μm or less,furthermore 40 μm or less, and in particular 30 μm or less.

The specific surface area by the BET method of the graphite material isusually 0.5 m²/g or more, preferably 0.7 m²/g or more, more preferably1.0 m²/g or more, and further preferably 1.5 m²/g or more, and usually25.0 m²/g or less, preferably 20.0 m²/g or less, more preferably 15.0m²/g or less, and further preferably 10.0 m²/g or less.

Moreover, in the case where Raman spectrometry by using argon laserlight is conducted with respect to the graphite material, it ispreferable that the intensity ratio I_(A)/I_(B) of the intensity I_(A)of a peak P_(A) detected within the range of 1,580 to 1,620 cm⁻¹ to theintensity I_(B) of a peak P_(B) detected within the range of 1,350 to1,370 cm⁻¹ is 0 or more, and 0.5 or less. In addition, the full width athalf maximum of the peak P_(A) is preferably 26 cm⁻¹ or less, and morepreferably 25 cm⁻¹ or less.

Besides the above-described various carbon materials, other materialscapable of absorbing and releasing lithium can also be used as thenegative electrode active material.

Specific examples of negative electrode active materials other thancarbon materials include metal oxides, e.g., tin oxide and siliconoxide, nitrides, e.g., Li_(2.6)Co_(0.4)N, lithium simple substance, andlithium alloys, e.g., lithium aluminum alloys. One type of thesematerials other than the carbon materials may be used alone or at leasttwo types may be used in combination. Alternatively, combinations withthe above-described carbon materials may be employed.

Usually, in a manner similar to that in the positive electrode activematerial layer, the negative electrode active material layer can beproduced by applying a slurry, in which the above-described negativeelectrode active material, a binder, and if necessary an electricallyconductive material and a thickener are made into a slurry with a liquidmedium, to a negative electrode collector, and conducting drying. As forthe liquid medium for forming the slurry, the binder, the thickener, theelectrically conductive material, and the like, the same substances asthose described above with respect to the positive electrode activematerial layer can be used.

<Non-Aqueous Electrolyte>

As for the non-aqueous electrolyte, for example, known organicelectrolytic solutions, polymer solid electrolytes, gel electrolytes,inorganic solid electrolytes, and the like can be used. Most of all,organic electrolytic solutions are preferable. The organic electrolyticsolution is formed by dissolving a solute (electrolyte) into an organicsolvent.

Here, the type of organic solvent is not specifically limited. Forexample, carbonates, ethers, ketones, sulfolane based compounds,lactones, nitriles, chlorinated hydrocarbons, amines, esters, amides,phosphoric acid ester compounds, and the like can be used. Typicalexamples include dimethyl carbonate, diethyl carbonate, ethyl methylcarbonate, propylene carbonate, ethylene carbonate, vinylene carbonate,vinyl ethylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran,1,4-dioxane, 4-methyl-2-pentanone, 1,2-dimethoxyethane,1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane,4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane,acetonitrile, propionitrile, benzonitrile, butyronitrile, valeronitrile,1,2-dichloroethane, dimethylformamide, dimethylsulfoxide, trimethylphosphate, and triethyl phosphate. Regarding these compounds, a part ofhydrogen atoms may be substituted with halogen atoms. These solvents canbe used alone or mixed solvents of at least two types can be used.

It is preferable that the above-described organic solvent is allowed tocontain a high dielectric constant solvent in order to dissociate anelectrolytic salt. Here, the high dielectric constant solvent refers toa compound having a relative dielectric constant of 20 or more at 25° C.It is preferable that among the high dielectric constant solvents,ethylene carbonate, propylene carbonate, and compounds in which hydrogenatoms thereof are substituted with other elements, e.g., halogen, oralkyl groups and the like are contained in the electrolytic solution.The proportion constituted by the high dielectric constant solvent inthe electrolytic solution is preferably 20 percent by weight or more,further preferably 25 percent by weight or more, and most preferably 30percent by weight or more. If the content of the high dielectricconstant solvent is less than the above-described range, a desiredbattery characteristics may not be obtained.

Furthermore, additives, for example, gases, e.g., CO₂, N₂O, CO, andSO_(z), vinylene carbonate, and polysulfide S_(x) ²⁻, which formfavorable coating films enabling efficient charge and discharge oflithium ions on a negative electrode surface, may be added at any ratioto the organic electrolytic solution. Regarding such additives, most ofall, vinylene carbonate is preferable.

The type of electrolytic salt is not specifically limited, and anypreviously known solute can be used. Specific examples include LiClO₄,LiAsF₆, LiPF₄, LiBF₄, LiB(CH₅)₄, LiBOB, LiCl, LiBr, CH₃SO₃Li, CF₃SO₃Li,LiN(SO₂CF₃)₂, LiN(SO₂C₂F₅)₂, LiC(SO₂CF₃)₃, and LiN(SO₃CF₃)₂. Any onetype of these electrolytic salt may be used alone or at least two typesmay be used together in any combination at any ratio.

A lithium salt serving as the electrolytic salt is contained in theelectrolytic solution in such a way that the content becomes usually 0.5mol/L or more, and 1.5 mol/L or less. If the lithium salt concentrationin the electrolytic solution is less than 0.5 mol/L or exceeds 1.5mol/L, the electrical conductivity is reduced and the batterycharacteristics may be adversely affected. It is preferable that thelower limit of this concentration is 0.75 mol/L or more, and the upperlimit is 1.25 mol/L or less.

Likewise, in the case where the polymer solid electrolyte is used, thetype thereof is not specifically limited, and any crystalline-amorphousinorganic substance known as a solid electrolyte can be used. Examplesof crystalline inorganic solid electrolytes include LiI, Li₃N,Li_(1+x)J_(x)Ti_(2-x)(PO₄)₃ (J=Al, Sc, Y, La), andLi_(0.5-3x)RE_(0.5+x)TiO₃ (RE=La, Pr, Nd, Sm). Furthermore, examples ofamorphous inorganic solid electrolytes include oxide glass, e.g.,4.9LiI-34.1Li₂O-61B₂O₅ and 33.3Li₂O-66.7SiO₂. Any one type of theseelectrolytes may be used alone or at least two types may be usedtogether in any combination at any ratio.

<Separator>

In the case where the above-described organic electrolytic solution isused as the electrolyte, a separator is interposed between the positiveelectrode and the negative electrode in order to prevent an occurrenceof short-circuit between the electrodes. The material and the shape ofthe separator are not specifically limited. However, it is preferablethat the stability toward the organic electrolytic solution used isensured, excellent liquid holding property is exhibited, and anoccurrence of short-circuit between electrodes can be preventedreliably. Preferable examples include fine porous films, sheets,nonwoven fabrics, and the like formed from various polymer materials.Specific examples of usable polymer materials include polyolefinpolymers, e.g., nylons, cellulose acetates, nitrocelluloses,polysulfones, polyacrylonitriles, polyvinylidene fluorides,polypropylenes, polyethylenes, and polybutenes. In particular,polyolefin polymers are preferable from the viewpoint of the chemicaland electrochemical stability which is an important factor of theseparator, and polyethylenes are particularly desirable from theviewpoint of the temperature of self locking which is one of thepurposes of use of the separator in the battery.

In the case where the separator formed from the polyethylene is used, itis preferable that an ultrahigh molecular weight polyethylene is usedfrom the viewpoint of high-temperature shape-maintaining property. Thelower limit of the molecular weight thereof is preferably 500,000,further preferably 1,000,000, and most preferably 1,500,000. On theother hand, the upper limit of the molecular weight is preferably5,000,000, further preferably 4,000,000, and most preferably 3,000,000.This is because if the molecular weight is too large, the fluiditybecomes too low and, thereby, the holes of the separator may not beclogged when being heated.

<Battery Shape>

The lithium secondary battery according to the present invention isproduced by assembling the above-described lithium secondary batterypositive electrode according to the present invention, the negativeelectrode, the electrolyte, and the separator used as necessary into anappropriate shape. Furthermore, other constituents, e.g., an outercasing, can be used, if necessary.

The shape of the lithium secondary battery according to the presentinvention is not specifically limited and can be selected appropriatelyfrom various shapes adopted generally in accordance with the usethereof. Examples of shapes adopted generally include a cylinder type inwhich sheet electrodes and a separator are made to be spiral, a cylindertype having an inside-out structure in which pellet electrodes and aseparator are combined, and a coin type in which pellet electrodes and aseparator are laminated. Furthermore, the method for assembling thebattery is not specifically limited and can be selected appropriatelyfrom various methods used usually in accordance with the shape of adesired battery.

Up to this point, general embodiments of the lithium secondary batteryaccording to the present invention have been described. However, thelithium secondary battery according to the present invention is notlimited to the above-described embodiments, but can be variouslymodified and executed within the bounds of the gist thereof.

EXAMPLES

The present invention will be described below in further detail withreference to the examples. However, the present invention is not limitedto these examples within the bounds of the gist thereof.

[Methods for Measuring Properties]

The individual properties and the like of lithium transition metal basedcompound powders produced in individual examples and comparativeexamples described later are measured as described below.

<Composition (Li/Ni/Mn/Co)>

ICP-AES analysis was conducted.

<Quantification of Additive Elements (Mo, W, Nb, B, Sn)>

ICP-AES analysis was conducted.

<Composition Analysis of Primary Grain Surface by X-Ray PhotoelectronSpectroscopy (XPS)>

An X-ray photoelectron spectroscope “ESCA-5700” produced by PhysicalElectronics, Inc., was used and the measurement was conducted under thefollowing condition.

X-ray source: monochromatic AlKα

Analysis area: 0.8 mm diameter

Take-off angle: 65°

Quantification method: areas of individual peaks of B1s, Mn2p_(1/2),Co2p_(3/2), Ni2p_(3/2), and W4f were corrected with a sensitivitycoefficient.

<Median Size of Secondary Grains>

The measurement was conducted after 5 minutes of ultrasonic dispersion.

<Average Primary Grain Size>

A SEM image magnified by 30,000 times was used for determination.

<Measurement of Various Properties by Mercury Penetration Method>

As for a measurement apparatus by the mercury penetration method,AutoPore III Model 9420 produced by Micromeritics was used. Regardingthe measurement condition in the mercury penetration method, themeasurement was conducted at room temperature while the pressure wasincreased from 3.86 kPa to 413 MPa. The value of surface tension ofmercury was assumed to be 480 dyn/cm, and the value of contact angle wasassumed to be 141.3°.

<Bulk Density>

The bulk density was determined as a powder packing density when 4 to 10g of sample powder was put into a 10 ml glass graduated cylinder andtapping was conducted 200 times at a stroke of about 20 mm.

<Specific Surface Area>

The specific surface area was determined by the BET method.

<Carbon Content C>

Carbon/Sulfur Analyzer EMIA-520 produced by HORIBA, Ltd., was used. Afew tens of mg to 100 mg of sample was weighed into a magnetic cruciblesubjected burning in advance, a supporting agent was added, combustionwas conducted with a high frequency furnace in an oxygen stream, andcarbon was extracted. Quantification of CO₂ in the combustion gas wasconducted by nondispersive infrared absorption spectrometry. As forsensitivity calibration, 150-15 Low alloy steel No. 1 (C certifiedvalue: 0.469 percent by weight) produced by the Japan Iron and SteelFederation was used.

<Volume Resistivity>

A powder resistivity measuring apparatus (Loresta GP resistivitymeasuring system PD-41: produced by Dia Instruments Co., Ltd) was used.The volume resistivity [Ω·cm] of a powder was measured under variouspressures with a powder probe unit (four-probe-ring electrode, electrodedistance of 5.0 mm, electrode radius of 1.0 mm, and sample radius of12.5 mm), where a sample weight was 3 g and an applied voltage limiterwas set at 90 V, and the values of volume resistivity at a pressure of40 MPa were compared.

<Identification of Crystal Phase (Layer Structure), Measurement of FullWidth at Half Maximum FWHM(110) Ascertainment of Presence and Absence ofHeterogeneous Phase Peak in (018), (110), (113) Diffraction Peaks andCalculation of Integrated Intensity and Integrated Intensity Ratio ofHeterogeneous Phase Peak/Intrinsic Crystal Phase Peak>

Powder X-ray diffractometry by using CuKα rays, as described below, wasconducted. Profile fitting was conducted with respect to (018), (110),(113) diffraction peaks originated from hexagonal system R−3m (No. 166)observed with respect to each sample, and the integrated intensity,integrated intensity ratio, and the like were calculated.

-   -   Full width at half maximum and the area were calculated by using        a diffraction pattern in the case where the measurement was        conducted at a fixed slit mode of a focusing beam method    -   Actual XRD measurement (examples, comparative examples) was        conducted at a variable slit mode and data conversion from        variable to fixed was conducted    -   Conversion from variable to fixed was conducted on the basis of        a calculation formula, intensity (fixed)=intensity        (valuable)/sin θ

(Specification of Powder X-Ray Diffraction Measuring Apparatus)

Apparatus name: X'Pert Pro MPD produced by PANalytical, the Nether lands

Optical system: focusing beam optical system

(Specification of Optical System)

Incident side: sealed X-ray tube (CuKα)

-   -   Soller Slit (0.04 rad)    -   Divergence Slit (Variable Slit)

Sample stage: rotating sample stage (Spinner)

Light receiving side: semiconductor array detector

(X'Celerator)

-   -   Ni-filter

Goniometer: 243 mm

(Measurement condition)

X-ray power (CuKα): 40 kV, 30 mA

Scanning axis: θ/2θ

Scanning range (2θ): 10.0°-75.0°

Measurement mode: Continuous

Reading width: 0.015°

Counting time: 99.7 sec

Automatic valuable slit (Automatic-DS: 10 mm (irradiation width))

Horizontal divergence mask: 10 mm (irradiation width)

<Median Size of Pulverized Grains in Slurry>

The median size was measured by using a known laserdiffraction/scattering grain size distribution measuring apparatus,where the refractive index was set at 1.24 and the reference of grainsize was on a volume basis. A 0.1 percent by weight sodiumhexametaphosphate aqueous solution was used as a dispersion medium, andthe measurement was conducted after 5 minutes of ultrasonic dispersion(output 30 W, frequency 22.5 kHz).

<Median Size as Average Grain Size of Raw Material Li₂CO₃ Powder>

The median size was measured by using a known laserdiffraction/scattering grain size distribution measuring apparatus(LA-920, produced by HORIBA, Ltd.), where the refractive index was setat 1.24 and the reference of grain size was on a volume basis. Ethylalcohol was used as a dispersion medium, and the measurement wasconducted after 5 minutes of ultrasonic dispersion (output 30 W,frequency 22.5 kHz).

<Properties of Grained Powder Obtained Through Spray-Drying>

The form was identified through SEM observation and cross-sectional SEMobservation. The median size serving as an average grain size and the 90percent cumulative diameter (D₉₀) were measured by using a known laserdiffraction/scattering grain size distribution measuring apparatus(LA-920, produced by HORIBA, Ltd.), where the refractive index was setat 1.24 and the reference of grain size was on a volume basis. A 0.1percent by weight sodium hexametaphosphate aqueous solution was used asa dispersion medium, and the measurement was conducted after 0 minutes,1 minute, 3 minutes, or 5 minutes of ultrasonic dispersion (output 30 W,frequency 22.5 kHz). The specific surface area was determined by the BETmethod. The bulk density was determined as a powder packing density when4 to 6 g of sample powder was put into a 10 ml glass graduated cylinderand tapping was conducted 200 times at a stroke of about 20 mm.

Production of Lithium Transition Metal Based Compound Powder (Examplesand Comparative Examples) Example 1

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, H₃BO₃,and WO₃ in such a way that a molar ratio becameLi:Ni:Mn:Co:B:W=1.12:0.45:0.45:0.10:0.005:0.010, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.15 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,140 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 7×10⁻³ L/min (gas liquidratio G/S=6,429). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 950° C. for 6 hours (temperature increase and decreaserate 3.33° C./min.). Thereafter, disintegration was conducted so as toobtain a lithium nickel manganese cobalt composite oxide (x=0.098,y=0.000, z=0.118) having a volume resistivity of 2.5×10⁶ Ω·cm, a carboncontent C of 0.064 percent by weight, and a composition ofLi_(1.118)(Ni_(0.451)Mn_(0.451)Co_(0.098))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, molar ratios of contained B and W were 0.39 percent bymole and 0.96 percent by mole, respectively. The average primary grainsize was 0.3 μm, the median size was 4.7 μm, the 90% cumulative diameter(D₉₀) was 7.0 μm, the bulk density was 1.2 g/cc, and the BET specificsurface area was 1.8 m²/g. Moreover, the atomic ratio of B (boron),(B/(Ni+Mn+Co)), of primary grain surface was 69 times larger than theatomic ratio of B of the whole grain, and the atomic ratio of W(tungsten), (W/(Ni+Mn+Co)), of primary grain surface was 6.0 timeslarger than the atomic ratio of W of the whole grain.

Example 2

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, H₃BO₃,and WO₃ in such a way that a molar ratio becameLi:Ni:Mn:Co:B:W=1.12:0.45:0.45:0.10:0.005:0.010, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.27 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 650 cp) was spray-dried by using a two-fluid nozzle type spraydryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Air was usedas a drying gas at this time, the amount G of introduction of drying gaswas specified to be 45 L/min, and the amount S of introduction of slurrywas specified to be 6×10⁻³ L/min (gas liquid ratio G/S=7,500). Thedrying inlet temperature was specified to be 150° C. About 15 g ofgrained powder obtained by spray drying with the spray dryer was putinto an alumina crucible, and firing was conducted in an air atmosphereat 1,000° C. for 6 hours (temperature increase and decrease rate 3.33°C./min.). Thereafter, disintegration was conducted so as to obtain alithium nickel manganese cobalt composite oxide (x=0.098, y=−0.007,z=0.129) having a volume resistivity of 1.5×10⁶ Ω·cm, a carbon content Cof 0.038 percent by weight, and a composition ofLi_(1.129)(Ni_(0.448)Mn_(0.454)Co_(0.098))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, molar ratios of contained B and W were 0.39 percent bymole and 0.96 percent by mole, respectively. The average primary grainsize was 0.6 μm, the median size was 4.1 μm, the 90% cumulative diameter(D₉₀) was 6.2 μm, the bulk density was 1.5 g/cc, and the BET specificsurface area was 1.0 m²/g. Moreover, the atomic ratio of B (boron),(B/(Ni+Mn+Co)), of primary grain surface was 134 times larger than theatomic ratio of B of the whole grain, and the atomic ratio of W(tungsten), (W/(Ni+Mn+Co)), of primary grain surface was 12 times largerthan the atomic ratio of W of the whole grain.

Example 3

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, H₃BO₃,and WO₃ in such a way that a molar ratio becameLi:Ni:Mn:Co:B:W=1.12:0.45:0.45:0.10:0.0025:0.005, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.38 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 750 cp) was spray-dried by using a two-fluid nozzle type spraydryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Air was usedas a drying gas at this time, the amount G of introduction of drying gaswas specified to be 45 L/min, and the amount S of introduction of slurrywas specified to be 6×10⁻³ L/min (gas liquid ratio G/S=7,500). Thedrying inlet temperature was specified to be 150° C. About 15 g ofgrained powder obtained by spray drying with the spray dryer was putinto an alumina crucible, and firing was conducted in an air atmosphereat 1,000° C. for 6 hours (temperature increase and decrease rate 3.33°C./min.). Thereafter, disintegration was conducted so as to obtain alithium nickel manganese cobalt composite oxide (x=0.097, y=−0.010,z=0.135) having a volume resistivity of 7.3×10⁵ Ω·cm, a carbon content Cof 0.038 percent by weight, and a composition ofLi_(1.135)(Ni_(0.447)Mn_(0.45)Co_(0.097))O₂. Furthermore, when a molarratio of total (Ni, Mn, Co) was assumed to be 1, molar ratios ofcontained B and W were 0.23 percent by mole and 0.51 percent by mole,respectively. The average primary grain size was 1.0 μm, the median sizewas 3.6 μm, the 90% cumulative diameter (D₉₀) was 5.7 μm, the bulkdensity was 1.3 g/cc, and the BET specific surface area was 0.8 m²/g.Moreover, the atomic ratio of B (boron), (B/(Ni+Mn+Co)), of primarygrain surface was 71 times larger than the atomic ratio of B of thewhole grain, and the atomic ratio of W (tungsten), (W/(Ni+Mn+Co)), ofprimary grain surface was 16 times larger than the atomic ratio of W ofthe whole grain.

Example 4

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, H₃BO₃,and WO₃ in such a way that a molar ratio becameLi:Ni:Mn:Co:B:W=1.12:0.45:0.45:0.10:0.0025:0.01, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.27 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,020 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 6×10⁻³ L/min (gas liquidratio G/S=7,500). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 1,000° C. for 6 hours (temperature increase anddecrease rate 3.33° C./min.). Thereafter, disintegration was conductedso as to obtain a lithium nickel manganese cobalt composite oxide(x=0.098, y=−0.004, z=0.134) having a volume resistivity of 3.0×10⁶Ω·cm, a carbon content C of 0.047 percent by weight, and a compositionof Li_(1.134)(Ni_(0.449)Mn_(0.453)Co_(0.098))O₂. Furthermore, when amolar ratio of total (Ni, Mn, Co) was assumed to be 1, molar ratios ofcontained B and W were 0.23 percent by mole and 1.00 percent by mole,respectively. The average primary grain size was 0.5 μm, the median sizewas 2.1 μm, the 90% cumulative diameter (D₉₀) was 3.9 μm, the bulkdensity was 1.2 g/cc, and the BET specific surface area was 1.5 m²/g.Moreover, the atomic ratio of B (boron), (B/(Ni+Mn+Co)), of primarygrain surface was 53 times larger than the atomic ratio of B of thewhole grain, and the atomic ratio of W (tungsten), (W/(Ni+Mn+Co)), ofprimary grain surface was 9.4 times larger than the atomic ratio of W ofthe whole grain.

Example 5

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, H₃BO₃,and WO₃ in such a way that a molar ratio becameLi:Ni:Mn:Co:B:W=1.05:0.333:0.333:0.333:0.005:0.005, conducting mixingand, thereafter, adding pure water thereto. Solid matters in theresulting slurry were pulverized until the median size became 0.31 μm byusing a circulating medium agitation type wet pulverizer while theslurry was agitated.

Subsequently, the resulting slurry (solid content 18 percent by weight,viscosity 830 cp) was spray-dried by using a two-fluid nozzle type spraydryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Air was usedas a drying gas at this time, the amount G of introduction of drying gaswas specified to be 45 L/min, and the amount S of introduction of slurrywas specified to be 6×10⁻³ L/min (gas liquid ratio G/S=7,500). Thedrying inlet temperature was specified to be 150° C. About 10 g ofgrained powder obtained by spray drying with the spray dryer was putinto an alumina crucible, and firing was conducted in an air atmosphereat 940° C. for 6 hours (temperature increase and decrease rate 3.33°C./min.). Thereafter, disintegration was conducted so as to obtain alithium nickel manganese cobalt composite oxide (x=0.333, y=−0.004,z=0.054) having a volume resistivity of 2.0×10⁶ Ω·cm, a carbon content Cof 0.031 percent by weight, and a composition ofLi_(1.054)(Ni_(0.332)Mn_(0.335)Co_(0.333))O₂. Furthermore, when a molarratio of total (Ni, Mn, Co) was assumed to be 1, molar ratios ofcontained B and W were 0.41 percent by mole and 0.50 percent by mole,respectively. The average primary grain size was 0.6 μm, the median sizewas 3.8 μm, the 90% cumulative diameter (D₉₀)) was 7.5 μm, the bulkdensity was 1.2 g/cc, and the BET specific surface area was 1.2 m²/g.Moreover, the atomic ratio of B (boron), (B/(Ni+Mn+Co)), of primarygrain surface was 73 times larger than the atomic ratio of B of thewhole grain, and the atomic ratio of W (tungsten), (W/(Ni+Mn+Co)), ofprimary grain surface was 15 times larger than the atomic ratio of W ofthe whole grain.

SERS Measurement

Regarding the lithium transition metal based compound powders obtainedin Examples 1 to 5, SERS was measured under the following measurementcondition. The resulting SERS patterns are shown in FIGS. 37 to 41,respectively.

<Method for Measuring SERS>

Apparatus: Nicoret Almega XR produced by Thermo Fisher Scientific

Pretreatment: silver evaporation (10 nm)

Excitation wavelength: 532 nm

Excitation output: 0.5 mW or less at position of sample

Analysis method: measurement of height and half-width of each peak, fromwhich linear back ground is excluded

Spectrum resolution: 10 cm⁻¹

The results thereof are collectively shown in Table 1 described below.

TABLE 1 Peak A Peak B Peak Half- Inten- intensity Position Intensitywidth Position sity ratio (cm⁻¹) (count) (cm⁻¹) (cm⁻¹) (count) B/AExample1 874 988 96 591 6924 0.14 Example2 865 570 91 589 3767 0.15Example3 864 218 88 587 2055 0.11 Example4 849 147 87 583 1787 0.08Example5 853 84 67 581 1334 0.06

Method for Measuring ToF-SIMS

Regarding the positive electrode active material obtained in Example 1,ToF-SIMS was measured under the following measurement condition. Theresulting ToF-SIMS pattern is shown in FIG. 42.

<Method for Measuring ToF-SIMS>

Apparatus: ToF-SIMS IV produced by ION-TOF

Primary ion: Bi₃ ⁺⁺

Acceleration voltage: 25 kV

Irradiation current: 0.1 pA

Irradiation area: 200 μm×200 μm

Integration time: 98 seconds

As shown in FIG. 42, six peaks originated from BWO₅ ⁻ were detectedwithin the mass number from 272 to 277 (FIG. 42 (a)). Furthermore, agroup of peaks originated from M′BWO₆ ⁻ were also detected, andparticularly intense five peaks were detected within the mass numberfrom 344 to 348 (FIG. 42 (b)).

Comparative Example 1

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, andLi₂WO₄ in such a way that a molar ratio becameLi:Ni:Mn:Co:W=1.10:0.45:0.45:0.10:0.005, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.16 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,720 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 6×10⁻³ L/min (gas liquidratio G/S=7,500). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 1,000° C. for 6 hours (temperature increase anddecrease rate 3.33° C./min.). Thereafter, disintegration was conductedso as to obtain a lithium nickel manganese cobalt composite oxide(x=0.097, y=0.003, z=0.114) having a volume resistivity of 5.4×10⁴ Ω·cm,a carbon content C of 0.042 percent by weight, and a composition ofLi_(1.114)(Ni_(0.453)Mn_(0.450)Co_(0.097))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, a molar ratio of contained W was 0.62 percent by mole.The average primary grain size was 0.4 μm, the median size was 1.4 μm,the 90% cumulative diameter (D₉₀) was 2.1 μm, the bulk density was 1.1g/cc, and the BET specific surface area was 2.1 m²/g. Moreover, theatomic ratio of W (tungsten), (W/(Ni+Mn+Co)), of primary grain surfacewas 9.8 times larger than the atomic ratio of W of the whole grain.

Comparative Example 2

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, andLi₂WO₄ in such a way that a molar ratio becameLi:Ni:Mn:Co:W=1.10:0.45:0.45:0.10:0.01, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.17 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,890 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 7×10⁻³ L/min (gas liquidratio G/S=6,429). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 1,000° C. for 6 hours (temperature increase anddecrease rate 3.33° C./min.). Thereafter, disintegration was conductedso as to obtain a lithium nickel manganese cobalt composite oxide(x=0.098, y=−0.002, z=0.139) having a volume resistivity of 4.7×10⁴Ω·cm, a carbon content C of 0.030 percent by weight, and a compositionof Li_(1.139)(Ni_(0.450)Mn_(0.452)Co_(0.098))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, a molar ratio of contained W was 1.03 percent by mole.The average primary grain size was 0.3 μm, the median size was 2.2 μm,the 90% cumulative diameter (D₉₀) was 3.9 μm, the bulk density was 1.0g/cc, and the BET specific surface area was 2.9 m²/g. Moreover, theatomic ratio of W (tungsten), (W/(Ni+Mn+Co)), of primary grain surfacewas 9.4 times larger than the atomic ratio of W of the whole grain.

Comparative Example 3

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, andLi₂WO₄ in such a way that a molar ratio becameLi:Ni:Mn:Co:W=1.10:0.45:0.45:0.10:0.02, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.13 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,910 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 7×10⁻³ L/min (gas liquidratio G/S=6,429). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 1,000° C. for 6 hours (temperature increase anddecrease rate 3.33° C./min.). Thereafter, disintegration was conductedso as to obtain a lithium nickel manganese cobalt composite oxide(x=0.097, y=0.012, z=0.124) having a volume resistivity of 1.1×10⁴ Ω·cm,a carbon content C of 0.050 percent by weight, and a composition ofLi_(1.124)(Ni_(0.457)Mn_(0.446)Co_(0.097))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, a molar ratio of contained W was 2.06 percent by mole.The average primary grain size was 0.2 μm, the median size was 0.8 μm,the 90% cumulative diameter (D₉₀) was 1.3 μm, the bulk density was 0.9g/cc, and the BET specific surface area was 3.8 m²/g. Moreover, theatomic ratio of W (tungsten), (W/(Ni+Mn+Co)), of primary grain surfacewas 6.0 times larger than the atomic ratio of W of the whole grain.

Comparative Example 4

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, and WO₃in such a way that a molar ratio becameLi:Ni:Mn:Co:W=1.10:0.45:0.45:0.10:0.005, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.17 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 14 percent by weight,viscosity 1,670 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 7×10⁻³ L/min (gas liquidratio G/S=6,429). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 1,000° C. for 6 hours (temperature increase anddecrease rate 3.33° C./min.). Thereafter, disintegration was conductedso as to obtain a lithium nickel manganese cobalt composite oxide(x=0.097, y=0.003, z=0.094) having a volume resistivity of 5.8×10⁴ Ω·cm,a carbon content C of 0.033 percent by weight, and a composition ofLi_(1.094)(Ni_(0.453)Mn_(0.450)Co_(0.097))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, a molar ratio of contained W was 0.51 percent by mole.The average primary grain size was 0.5 μm, the median size was 1.6 μm,the 90% cumulative diameter (D₉₀) was 2.4 μm, the bulk density was 1.0g/cc, and the BET specific surface area was 2.2 m²/g. Moreover, theatomic ratio of W (tungsten), (W/(Ni+Mn+Co)), of primary grain surfacewas 12 times larger than the atomic ratio of W of the whole grain.

Comparative Example 5

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, andLi₂B₄O₇ in such a way that a molar ratio becameLi:Ni:Mn:Co:B=1.10:0.45:0.45:0.10:0.005, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.16 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,460 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 6×10⁻³ L/min (gas liquidratio G/S=7,500). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 1,000° C. for 6 hours (temperature increase anddecrease rate 3.33° C./min.). Thereafter, disintegration was conductedso as to obtain a lithium nickel manganese cobalt composite oxide(x=0.099, y=−0.001, z=0.096) having a volume resistivity of 5.3×10⁴Ω·cm, a carbon content C of 0.047 percent by weight, and a compositionof Li_(1.096)(Ni_(0.450)Mn_(0.451)Co_(0.099))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, a molar ratio of contained B was 0.24 percent by mole.The average primary grain size was 1.0 μm, the median size was 5.9 μm,the 90% cumulative diameter (D₉₀) was 8.9 μm, the bulk density was 1.8g/cc, and the BET specific surface area was 0.8 m²/g. Moreover, theatomic ratio of B (boron), (B/(Ni+Mn+Co)), of primary grain surface was213 times larger than the atomic ratio of B of the whole grain.

Comparative Example 6

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, andH₃BO₃ in such a way that a molar ratio becameLi:Ni:Mn:Co:B=1.10:0.45:0.45:0.10:0.005, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.22 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,450 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 7×10⁻³ L/min (gas liquidratio G/S=6,429). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 950° C. for 6 hours (temperature increase and decreaserate 3.33° C./min.). Thereafter, disintegration was conducted so as toobtain a lithium nickel manganese cobalt composite oxide (x=0.100,y=−0.007, z=0.096) having a volume resistivity of 3.5×10⁴ Ω·cm, a carboncontent C of 0.065 percent by weight, and a composition ofLi_(1.096)(Ni_(0.447)Mn_(0.453)Co_(0.100))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, a molar ratio of contained B was 0.39 percent by mole.The average primary grain size was 0.2 μm, the median size was 5.5 μm,the 90% cumulative diameter (D₃₀) was 8.6 μm, the bulk density was 1.2g/cc, and the BET specific surface area was 1.8 m²/g. Moreover, theatomic ratio of B (boron), (B/(Ni+Mn+Co)), of primary grain surface was40 times larger than the atomic ratio of B of the whole grain.

Comparative Example 7

A slurry was prepared by weighing Li₂CO₃, Ni(OH)₂, Mn₃O₄, CoOOH, andHBO₃ in such a way that a molar ratio becameLi:Ni:Mn:Co:B=1.10:0.45:0.45:0.10:0.005, conducting mixing and,thereafter, adding pure water thereto. Solid matters in the resultingslurry were pulverized until the median size became 0.22 μm by using acirculating medium agitation type wet pulverizer while the slurry wasagitated.

Subsequently, the resulting slurry (solid content 15 percent by weight,viscosity 1,450 cp) was spray-dried by using a two-fluid nozzle typespray dryer (Model LT-8: produced by Ohkawara Kakohki Co., Ltd.). Airwas used as a drying gas at this time, the amount G of introduction ofdrying gas was specified to be 45 L/min, and the amount S ofintroduction of slurry was specified to be 7×10⁻³ L/min (gas liquidratio G/S=6,429). The drying inlet temperature was specified to be 150°C. About 15 g of grained powder obtained by spray drying with the spraydryer was put into an alumina crucible, and firing was conducted in anair atmosphere at 1,000° C. for 6 hours (temperature increase anddecrease rate 3.33° C./min.). Thereafter, disintegration was conductedso as to obtain a lithium nickel manganese cobalt composite oxide(x=0.100, y=0.007, z=0.110) having a volume resistivity of 5.8×10⁴ Ω·cm,a carbon content C of 0.033 percent by weight, and a composition ofLi_(1.110)(Ni_(0.447)Mn_(0.453)Co_(0.100))O₂ and having a layerstructure. Furthermore, when a molar ratio of total (Ni, Mn, Co) wasassumed to be 1, a molar ratio of contained B was 0.42 percent by mole.The average primary grain size was 0.8 μm, the median size was 5.3 μm,the 90% cumulative diameter (D₉₀) was 7.9 μm, the bulk density was 1.4g/cc, and the BET specific surface area was 1.0 m²/g. Moreover, theatomic ratio of B (boron), (B/(Ni+Mn+Co)), of primary grain surface was113 times larger than the atomic ratio of B of the whole grain.

The compositions and property values of the lithium transition metalbased compound powders produced in the above-described examples andcomparative examples are shown in Table 2, Table 3, Table 4, and Table5. Furthermore, the powder properties of the spray-dried substancesserving as firing precursors are shown in Table 6.

The pore distribution curves of the lithium nickel manganese cobaltcomposite oxides produced in Examples 1 to 5 and Comparative examples 1to 7 are shown in FIGS. 1 to 12, respectively. The SEM images(photographs) (magnification ×10,000) are shown in FIGS. 13 to 24,respectively, and the powder X-ray diffraction patterns are shown inFIGS. 25 to 36, respectively.

TABLE 2 Molar ratio Molar ratio (mol %) of (mol %) of Additive element 1Additive element 2 (B/Ni + Mn + Co) (W/Ni + Mn + Co) Positive electrodeAdditive Charge Analysis Additive Charge Analysis material element 1value value *1) element 2 value value *2) Example 1 B 0.5 0.39 69 W 10.96 6.0 2 B 0.5 0.39 134 W 1 0.96 12 3 B 0.25 0.23 71 W 0.5 0.51 16 4 B0.25 0.23 53 W 1.0 1.00 9.4 5 B 0.5 0.41 73 W 0.5 0.50 15 Comparative 1— — — — W 0.5 0.62 9.8 example 2 — — — — W 1 1.03 9.4 3 — — — — W 2 2.066 4 — — — — W 0.5 0.51 12 5 B 0.5 0.24 213 — — — — 6 B 0.5 0.39 40 — — —— 7 B 0.5 0.42 113 — — — — *1) Ratio of an atomic ratio of Additiveelements 1 in total to a total of metal elements other than Li. Additiveelements 1, and Additive elements 2 of a surface portion of a primarygrain to the atomic ratio of the whole primary grain *2) Ratio of anatomic ratio of Additive elements 2 in total to a total of metalelements other than Li. Additive elements 1, and Additive elements 2 ofa surface portion of a primary grain to the atomic ratio of the wholeprimary grain

TABLE 3 BET Amount of Partial pore Average 90% specific Positive mercuryPore radius (nm) volume (ml/g) primary Median Cumulative Bulk surfaceelectrode penetration*³⁾ Peak Peak Peak Peak grain size size diameterdensity area Judge- material (ml/g) top 1*⁴⁾ top 2*⁵⁾ top 1*⁴⁾ top 2*⁵⁾(μm) (μm) (D₉₀) (μm) (g/cm³) (m²/g) ment Example 1 0.88 258 941 0.140.45 0.3 4.7 7 1.2 1.8 ◯ 2 0.53 259 944 0.04 0.36 0.6 4.1 6.2 1.5 1 ◯ 30.74 329 1448 0.03 0.44 1.0 3.6 5.7 1.3 0.8 ◯ 4 0.83 330 941 0.10 0.490.5 2.1 3.9 1.2 1.5 ◯ 5 0.89 328 1206 0.07 0.43 0.6 3.8 7.5 1.2 1.2 ◯Compar- 1 0.91 — 400, 620 — 0.48 0.4 1.4 2.1 1.1 2.1 X ative 2 1.05 —401, 621 — 0.59 0.3 2.2 3.9 1 2.9 X example 3 1.07 259 494 0.36 0.18 0.20.8 1.3 0.9 3.8 X 4 0.88 — 494 — 0.44 0.5 1.6 2.4 1 2.2 X 5 0.49 — 1210— 0.3 1 5.9 8.9 1.8 0.8 ◯ 6 0.84 170 941 0.14 0.41 0.2 5.5 8.6 1.2 2.8 X7 0.57 209 1447 0.01 0.34 0.8 5.3 7.9 1.4 1 ◯ *³⁾The amount of mercurypenetration during pressurization from a pressure of 3.86 kPa to 413 MPain a measurement based on a mercury penetration method *⁴⁾Related tosubpeaks observed at 80 nm or more, and less than 300 nm or less (poreradius) or 300 nm or more, and less than 400 nm (pore radius) in a poredistribution curve *⁵⁾Related to main peak observed at 300 nm or more(pore radius) in a pore distribution curve

TABLE 4 Carbon Positive Composition content C Volume electrode Lowerlimit Upper limit (percent by resistivity material x y z of z *6) of z*7) weight) (Ω · cm) Judgement Example 1 0.098 0.000 0.118 0.045 0.1800.084 2.5 × 10⁵ ◯ 2 0.098 −0.007 0.129 0.051 0.186 0.038 1.5 × 10⁵ ◯ 30.097 −0.010 0.135 0.054 0.188 0.038 7.3 × 10⁵ ◯ 4 0.098 −0.004 0.1340.049 0.184 0.047 3.0 × 10⁶ ◯ 5 0.333 −0.004 0.054 0.016 0.136 0.031 2.0× 10⁸ ◯ Comparative example 1 0.097 0.003 0.114 0.042 0.178 0.042 5.4 ×10⁴ ◯ 2 0.098 −0.002 0.139 0.047 0.182 0.030 4.7 × 10⁴ ◯ 3 0.097 0.0120.124 0.035 0.171 0.050 1.1 × 10⁴ ◯ 4 0.097 0.003 0.094 0.042 0.1780.033 5.8 × 10⁴ ◯ 5 0.099 −0.001 0.096 0.046 0.181 0.047 5.3 × 10⁴ ◯ 60.100 −0.007 0.096 0.051 0.186 0.065 3.5 × 10⁴ X 7 0.100 −0.007 0.1100.051 0.186 0.033 5.8 × 10⁴ ◯ *6) When 0 ≦ x ≦ 0.1, (1 − x)(0.05 −0.98y), and when 0.1 < x ≦ 0.35, (1 − x)(0.02 − 0.98y) *7) (1 − x)(0.20− 0.88y)

TABLE 5 Positive electrode FWHM Integrated intensity Integratedintensity ratio material (110) I₀₁₈ (I₀₁₈) I₁₁₀ (I₁₁₀) I₁₁₃ (I₁₁₃)I₀₁₈/I₀₁₈ I₁₁₀/I₁₁₀ I₁₁₃/I₁₁₃ Example 1 0.219 1908(178) 1821(202)845(137) 0.092 0.111 0.182 2 0.178 1964 (64)  1854 (105) 1009 (42) 0.033 0.57 0.042 3 0.156 1898 1747 (148) 862 (207) 0 0.084 0.240(heterogenous phase is not detected) 4 0.185 1787 (230) 1893 (261) 904(115) 0.130 0.154 0.127 5 0.129 1639 1622  951 0 0 0 (heterogenous phase(heterogenous phase (heterogenous phase is not detected) is notdetected) is not detected) Comparative example 1 0.169 2248 2184 1118 00 0 (heterogenous phase (heterogenous phase (heterogenous phase is notdetected) is not detected) is not detected) 2 0.193 2239 2062 (160) 1049(73)  0 0.078 0.07 (heterogenous phase is not detected) 3 0.339 20882043 (50) 786 (397) 0 0.024 0.518 (heterogenous phase is not detected) 40.169 2123 2112 1081 0 0 0 (heterogenous phase (heterogenous phase(heterogenous phase is not detected) is not detected) is not detected) 50.137 2201 2156 1134 0 0 0 (heterogenous phase (heterogenous phase(heterogenous phase is not detected) is not detected) is not detected) 60.477 1373 (711) 1588 (445) 698 (380) 0.518 0.28 0.517 7 0.175 2117 20721083 0 0 0 (heterogenous phase (heterogenous phase (heterogenous phaseis not detected) is not detected) is not detected)

TABLE 6 Powder properties of spray-dried substance BET specific PositiveMedian size (μm) *8) Bulk surface electrode US US US US density areamaterial 0 min. 1 min. 3 min. 5 min. (g/cm³) (m²g) Example 1 6.4 4.7 0.50.4 0.9 59.7 2 5.3 1.0 0.3 0.3 0.9 55.5 3 5.7 3.6 0.5 0.4 0.9 44.3 4 5.63.3 0.4 0.4 0.9 54.5 5 6.5 4.7 1.5 0.7 0.9 68.3 Compar- 1 6.4 5.8 4.11.9 0.9 59.8 ative 2 6.7 6.0 4.4 0.8 0.9 60.4 example 3 6.5 5.3 2.7 0.50.9 58.5 4 6.4 5.1 2.5 0.5 0.9 59.5 5 7.6 5.7 2.9 1.6 0.9 59.4 6 7.8 5.40.5 0.4 0.9 57.8 7 7.8 5.4 0.5 0.4 0.9 57.8 *8) US represents atreatment by ultrasonic dispersion “Ultra Sonic dispersion”, and thefollowing numerical value represents a treatment time (minute).

[Preparation of Battery and Evaluation]

Each of the lithium transition metal based compound powders produced inExamples 1 to 5 and Comparative examples 1 to 7 described above was usedas a positive electrode material (positive electrode active material). Alithium secondary battery was prepared by the following method andevaluation was conducted.

(1) Rate Test:

Regarding each of the lithium transition metal based compound powdersproduced in Examples 1 to 5 and Comparative examples 1 to 7, 75 percentby weight of the compound powder, 20 percent by weight of acetyleneblack, and 5 percent by weight of polytetrafluoroethylene powder wereweighed and mixed with a mortar sufficiently. The resulting mixture wasshaped into a sheet and subjected to punching with a punch of 9 mmdiameter. At this time, the whole weight was adjusted to become about 8mg. This was contact-bonded to an aluminum expanded metal so as toproduce a positive electrode of 9 mm diameter.

A coin type cell was assembled by using the resulting positive electrodeof 9 mm diameter as a test electrode, a lithium metal sheet as a counterelectrode, and an electrolytic solution in which 1 mol/L of LiPF_(E) wasdissolved into a solvent of EC (ethylene carbonate):DMC (dimethylcarbonate):EMC (ethyl methyl carbonate)=3:3:4 (volume ratio), wherein aporous polyethylene film of 25 μm thickness was used as a separator.

Regarding the resulting coin type cell, in initial 2 cycles, an upperlimit charge voltage was set at 4.4 V, constant-current-constant-voltagecharge (constant-current charge at a current density: 0.137 mA/cm²(0.1C) was conducted up to 4.4 V and, thereafter, constant-voltagecharge was conducted until 0.01C was reached) was conducted.Subsequently, a lower limit discharge voltage was set at 3.0 V, andconstant-current discharge (current density 0.137 mA/cm² (0.1C)) wasconducted. Furthermore, in 3rd to 10th cycle, the test was conducted,wherein constant-current-constant-voltage charge at 0.2C(constant-current charge at 0.2C was conducted up to 4.4 V and,constant-voltage charge was conducted until 0.01C was reached) wasconducted, and constant-current discharge at each of 0.1C, 0.2C, 0.5C,1C, 3C, 5C, 7C, and 9C was conducted. Here, the current corresponding to1C was assumed to be 150 mA per gram of active material. At this time,the 0.1C discharge capacity (mAh/g) in the 1st cycle (initial dischargecapacity), 0.1C discharge capacity (mAh/g) in the 3rd cycle (3rd cycledischarge capacity [a]), 1C discharge capacity (mAh/g) in the 6th cycle(6th cycle discharge capacity [b]), and 9C discharge capacity (mAh/g) inthe 10th cycle (10th cycle discharge capacity [c]) were examined. Theresults are shown in Table 7.

As for the acceptance standard for judgment in Examples, the initialdischarge capacity in the above-described 1st cycle was set at 170 mAh/gor more, the 0.1C discharge capacity in the 3rd cycle was set at 170mAh/g or more, the 1C discharge capacity in the 6th cycle was set at 155mAh/g or more, and the 9C discharge capacity in the 10th cycle was setat 120 mAh/g or more.

(2) Low-Temperature Load Characteristic Test:

Regarding each of the layer lithium nickel manganese cobalt compositeoxide powders produced in Examples 1 to 5 and Comparative examples 1 to7, 75 percent by weight of the compound powder, 20 percent by weight ofacetylene black, and 5 percent by weight of polytetrafluoroethylenepowder were weighed and mixed with a mortar sufficiently. The resultingmixture was shaped into a thin sheet and was subjected to punching withpunches of 9 mm diameter and 12 mm diameter. At this time, the wholeweights were adjusted to become about 8 mg and about 18 mg,respectively. They were contact-bonded to aluminum expanded metals so asto produce positive electrodes of 9 mm diameter and 12 mm diameter. Thepositive electrodes of 9 mm diameter and 12 mm diameter are referred toas “positive electrode A” and “positive electrode B”, respectively.

A coin type cell was assembled by using the positive electrode A of 9 mmdiameter as a test electrode, a lithium metal sheet as a counterelectrode, and an electrolytic solution in which 1 mol/L of LiPFe wasdissolved into a solvent of EC (ethylene carbonate):DMC (dimethylcarbonate):EMC (ethyl methyl carbonate)=3:3:4 (volume ratio), wherein aporous polyethylene film of 25 μm thickness was used as a separator.

Regarding the resulting coin type cell,constant-current·constant-voltage charge, that is, a reaction in whichlithium ions were released from the positive electrode, at 0.2 mA/cm²was conducted while the upper limit was set at 4.2 V. Subsequently, theinitial charge capacity per unit weight of positive electrode activematerial at 0.2 mA/cm² was assumed to be Qs(C) [mAh/g] and the initialdischarge capacity was assumed to be Qs(D) [mAh/g].

A graphite powder (d₀₀₂=3.35 Å) having an average grain size of 8 to 10μm was used as a negative electrode active material, and polyvinylidenefluoride was used as a binder. They were weighed at a weight ratio of92.5:7.5, this was mixed in a N-methylpyrrolidone solution so as toprepare a negative electrode mistura slurry. The resulting slurry wasapplied to one surface of copper foil of 20 μm thickness and was driedso as to vaporize the solvent. Thereafter this was punched into adiameter of 12 mm, and was subjected to a press treatment at 0.5 ton/cm²(49 MPa), so that a negative electrode B was prepared. At this time, theamount of the negative electrode active material on the electrode wasadjusted to become about 5 to 12 mg.

A battery cell was assembled by using the resulting negative electrode Bas a test electrode and a lithium metal as a counter electrode. A testin which the negative electrode was allowed to absorb lithium ions by aconstant current-constant voltage method (cut current 0.05 mA) at 0.2mA/cm²-3 mV was conducted where the lower limit was set at 0 V, and theinitial absorption capacity per unit weight of negative electrode activematerial at that time was assumed to be Qf [mAh/g].

The above-described positive electrode B and the negative electrode Bwere combined, a test battery was assembled by using coin cell, and thebattery performance was evaluated. That is, the above-described positiveelectrode B prepared was placed on a positive electrode can of the coincell, a porous polyethylene film of 25 μm thickness serving as aseparator was placed thereon, and held with a polypropylene gasket.Thereafter, an electrolytic solution in which 1 mol/L of LiPF₆ wasdissolved into a solvent of EC (ethylene carbonate):DMC (dimethylcarbonate):EMC (ethyl methyl carbonate)=3:3:4 (volume ratio) was used asa non-aqueous electrolytic solution, and this was added into the can andwas allowed to penetrate into the separator sufficiently. Subsequently,the above-described negative electrode B was placed, a negativeelectrode can was placed so as to seal and, thereby, a coin type lithiumsecondary battery was prepared. At this time, the balance between theweight of the positive electrode active material and the weight of thenegative electrode active material was set in such a way as tosubstantially satisfy the following formula.

weight of positive electrode active material [g]/weight of negativeelectrode active material [g]=(Qf [mAh/g]/1.2)Qs(C) [mAh/g]

In order to measure the low-temperature load characteristics of the thusobtained battery, one hour rate current value, that is, 1C, of thebattery was set as represented by the following formula, and a test wasconducted as described below.

1C [mA]=Qs(D)×weight of positive electrode active material [g]/h

Initially, two cycles of 0.2C constant-current charge and discharge andone cycle of 1C constant-current charge and discharge were conducted atroom temperature. The upper limit of charge was specified to be 4.1 V,and the lower limit voltage was specified to be 3.0 V. Next, the stateof charge of the coin cell was adjusted at 40% through ⅓ Cconstant-current charge and discharge, and the coin cell was kept in alow-temperature atmosphere at −30° C. for 1 hour or more. Thereafter,when constant-current discharge was conducted at 0.5C [mA] for 10seconds, the resistance value R [Ω] was calculated from the followingformula, where the voltage after 10 seconds was assumed to be V [mV],the voltage before the discharge was assumed to be V₀ [mV], and ΔV=V−V₀.

R [Ω]=ΔV [mV]/0.5C [mA]

Table 7 shows resistance values measured with respect to batteries byusing the lithium nickel manganese cobalt composite oxides in Examples 1to 5 and Comparative examples 1 to 7 as respective positive electrodeactive materials. A smaller resistance value indicates that thelow-temperature load characteristics are better. The acceptance standardfor judgment in Examples was set in such a way that the resistance valuewas 480Ω or less.

TABLE 7 Initial discharge 3rd cycle discharge 10th cycle discharge Low-Positivex capacity capacity [a] 6th cycle discharge capacity [c]temperature electrode (mAh/g)/3.0-4.4 V, (mAh/g)/3.0-4.4 V, capacity [b](mAh/g)/3.0-4.4 V, resistance Judgement material 0.1 C 0.1 C(mAh/g)/3.0-4.4 V, 1 C 9 C (Ω) result Example 1 171 171 156 121 384 ◯ 2172 173 159 124 349 ◯ 3 171 172 158 123 405 ◯ 4 174 174 160 124 342 ◯ 5178 177 167 145 220 ◯ Comparative 1 177 177 165 133 406 ◯ example 2 176176 165 131 346 ◯ 3 171 171 159 130 325 ◯ 4 178 178 164 126 413 ◯ 5 175176 154 109 639 X 6 170 189 156 124 439 ◯ 7 175 176 159 120 538 X

As is clear from Table 7, according to the lithium nickel manganesecobalt based composite oxide powder and the like for a lithium secondarybattery positive electrode material of the present invention, a lithiumsecondary battery exhibiting excellent load characteristics can berealized.

The present invention has been described in detail with reference tospecific forms. However, it should be understood by those skilled in theart that various modifications could be made without departing from thespirit or scope of the invention.

The present invention contains subject matter related to Japanese PatentApplication (Japanese Patent Application No. 2006-349912) filed on Dec.26, 2006 and Japanese Patent Application (Japanese Patent ApplicationNo. 2007-79360) filed on Mar. 26, 2007, the entire contents of which areincorporated herein by reference.

1-51. (canceled)
 52. A lithium transition metal based compound powdersuitable for a lithium secondary battery positive electrode material,comprising, as a primary component, a lithium transition metal basedcompound represented by formula (I):LiMO₂  (1) wherein M in formula (I) is represented by formula (II′):M=Li_(z/(2+z′)){(Ni_((1+y′)/2)Mn_((1−y′)/2))_(1-x)Co_(x′)}_(2/(2+z′))  (II′)wherein 0.1<x′≦0.35 −0.1≦y′≦0.1(1−x′)(0.02−0.98y′)≦z′≦(1−x′)(0.20−0.88y′), wherein the lithiumtransition metal based compound powder enables insertion and eliminationof lithium ions when incorporated into a lithium secondary batterypositive electrode, wherein the lithium transition metal based compoundpowder has a peak A between 800 cm⁻¹ or more and 900 cm⁻¹ or less in asurface enhanced Raman spectrum wherein the half-width of the peak A is30 cm⁻¹ or more in a surface enhanced Raman spectrum, wherein thelithium transition metal based compound powder includes primary grains,wherein B and W are contained in a surface of the primary grains,wherein the total amount of B and W relative to the total amount oftransition metal elements in the lithium transition metal based compoundrepresented by the formula (I) is from 0.01 to less than 2 percent bymol, and wherein the ratio of B to W is from 10:1 to 1:20.
 53. Thelithium transition metal based compound powder of claim 52, wherein theintensity of the peak A to the intensity of a peak B in the vicinity of600±50 cm⁻¹ is larger than 0.04 in a surface enhanced Raman spectrum.54. The lithium transition metal based compound powder of claim 52,wherein the amount of mercury penetration is between 0.4 cm³/g or moreand 1.5 cm³/g or less during pressurization from a pressure of 3.86 kPato 413 MPa in a mercury penetration curve based on a mercury penetrationmethod.
 55. The lithium transition metal based compound powder of claim52, wherein a pore distribution curve based on the mercury penetrationmethod has at least one main peak with a peak top present at a poreradius of between 300 nm or more and 1,500 nm or less and has a subpeakwith a peak top present at a pore radius of between 80 nm or more andless than 300 nm.
 56. The lithium transition metal based compound powderof claim 52, wherein regarding a pore distribution curve based on themercury penetration method, the pore volume related to the peak with apeak top present at a pore radius of between 300 nm or more and 1,500 nmor less is between 0.3 cm³/g or more and 0.8 cm³/g or less and the porevolume related to the subpeak with a peak top present at a pore radiusof between 80 nm or more and less than 300 nm is between 0.01 cm³/g ormore and 0.3 cm³/g or less.
 57. The lithium transition metal basedcompound powder of claim 52, wherein a pore distribution curve based onthe mercury penetration method has at least one main peak with a peaktop present at a pore radius of between 400 nm or more and 1,500 nm orless and has a subpeak with a peak top present at a pore radius ofbetween 300 nm or more and less than 400 nm.
 58. The lithium transitionmetal based compound powder of claim 52, wherein the volume resistivityis between 1×10³ Ω·cm or more and 1×10⁷ Ω·cm or less when compaction isconducted at a pressure of 40 MPa.
 59. The lithium transition metalbased compound powder of claim 52, which contains from 0.005 percent byweight to 0.25 percent by weight of carbon.
 60. The lithium transitionmetal based compound powder of claim 52, wherein when the full width athalf maximum of a (110) diffraction peak present at a diffraction angle2θ in the vicinity of 64.5° in powder X-ray diffractometry by using CuKαrays is FWHM(110), then 0.01<FWHM(110)≦0.3.
 61. A method formanufacturing the lithium transition metal based compound powder ofclaim 52, comprising pulverizing a lithium compound, a nickel compound,a manganese compound, a cobalt compound, a boron compound and a tungstencompound in a liquid medium, spray-drying a slurry in which thecompounds are dispersed homogeneously, and firing the resultingspray-dried substance.
 62. The method of claim 61, wherein the lithiumcompound, nickel compound, manganese compound, cobalt compound, boroncompound and tungsten compound are pulverized in the liquid medium untilthe median particle size measured with a laser diffraction/scatteringgrain size distribution measuring apparatus after 5 minutes ofultrasonic dispersion (output 30 W, frequency 22.5 kHz) reaches 0.4 μmor less, where the refractive index is set at 1.24 and the reference ofgrain size is on a volume basis, and spray drying is conducted under acondition in which 50 cp≦V≦4,000 cp and 500≦G/S≦10,000 hold, where V(cp) represents a slurry viscosity, S (L/min) represents an amount ofsupply of slurry, and G (L/min) represents an amount of supply of gas inthe spray drying.
 63. The method of claim 61, wherein the spray-driedsubstance is fired at a firing temperature of 900° C. or higher in anoxygen-containing gas atmosphere.
 64. The method of claim 61, whereinthe lithium compound is lithium carbonate.
 65. A lithium secondarybattery positive electrode comprising a positive electrode activematerial layer containing the lithium transition metal based compoundpowder of claim 52, and a binder on a collector.
 66. A lithium secondarybattery comprising a negative electrode capable of absorbing andreleasing lithium, a non-aqueous electrolyte containing a lithium salt,and the lithium secondary battery positive electrode according to claim65.